Thanks! I appreciate that background.
To put it into layman’s terms (and try out an explanation I may use for my patients):
Think of sending a text message to a friend A. This message would be messenger RNA. Your brain is the DNA that composes the message (the phone would be tRNA).You can send as many messages as you like daily. Now you are out with friend B who wants to contact A but forgot his phone. He asks to borrow your phone. He then sends a message to A using your phone. A may or may not delete the messages immediately but it doesn’t change your email messages. Friend A receives all of your messages and will continue to read them. There is no change to your brain (DNA) the phone (tRNA) or any of your messages, which you can continue to send. The only difference is that Friend A has now received an additional message from Friend B using your phone. (And to avoid nitpicking just assume that Friend B sends the message from his own email).
If A sends a text from my phone, it does change my messages because it shows up in both of our conversations as coming from me. Which is important because anything coming from my phone number is assumed to be my message. As I understand it message RNA is more like a text than an email. With emails you are usually shown the header information, with texts the headers are technically there but they are hidden from view, and with RNA I don’t think there is anything identifying the source, it’s just a molecule assumed to come from the cell’s nucleus.
It’s like if Friend A is out shopping with my charge card, Friend A is the part of the cell that makes proteins and the charge card represents the cell’s resources. I might tell Friend A to get some eggs or paper towels or something. Friend B is the doctor or EMT giving the injection, in the analogy she sends a message to pick up medicine that will help your body deal with a future infection. The medicine is the spike protein, I guess. In doing so she changes my messages but for a good purpose, she doesn’t prevent me from sending other messages and she doesn’t change any individual messages I already sent.
~Max
Don’t let the CDC text you!
That’s just one way they get the toxic spike proteins into your body. 
Something to keep in mind because I’m not sure you understand it based on your posts (apologies if I read wrong), the mRNA vaccine basically pushes lipid-encased material into your body, when your body’s cells near the injection cite interact with those lipid encased materials, those cells now can use the mRNA in the lipid and run the “commands” in the mRNA, which in this case means generating spike proteins akin to those that SARS-CoV-2 has. (The lipid shell is very important and complex and without it we couldn’t utilize messenger RNA like this.)
This article has a lot of details in mostly layman friendly terms about the lipids and how they enable moving mRNA from outside the body into the body in a form that we can transmit to our cells to use: Without these lipid shells, there would be no mRNA vaccines for COVID-19 (acs.org)
But here’s something key to understand–your body has a very large number of cells, only a very small number come into contact with the lipid encased mRNA, proportionally speaking. So in general only in a very limited sense (using your terminology) has your “RNA changed”, it changed temporarily at a very small site of your overall body. Inside the cells themselves the mRNA breaks down fairly quickly and those cells no longer produce spike proteins and no longer have the “instructions” to do so. The spike proteins themselves exist for a while, but are gradually destroyed by the immune system and also break down on their own over time. The mRNA vaccines do not work long term because they’ve taught your body to make spike protein, the very, very small part of your body that has learned how to make spike protein loses that ability fairly quickly, and the resulting spike proteins go away in what’s believed to be a few weeks after that. The key is that the immune system’s reaction to the presence of the spike protein becomes part of your immune system’s “learned response” to known/previously encountered pathogens. So, if it ever sees that spike protein signature again, it’s going to know and go at it much more effectively, if that spike protein it sees next time is from the covid virus in your body, it’s going to have a much greater chance of destroying them before they cause any sort of systemic illness. Note that the injections are given into your muscle, and the immune response at those spike proteins often causes a localized inflammation of the surrounding tissue–hence pain and soreness, a fairly common thing from the immune process.
I think I understand this concept. Hopefully. 
The doc at work actually ordered polyethylene glycol testing for a patient earlier this week, the rationale being that she may have developed an allergic response to that component of the vaccine’s lipid shell.
I have no idea how many blood cells of the type that could absorb the vaccine actually do, given a standard dose. I’m not even sure whether it’s only blood cells or if other types of cells will take in vaccine, but I assume it’s only blood cells. Probably a few absorb more than one lipid-encased mRNA molecule.
But I acknowledge your point, that most cells in the body never come in contact with the vaccine. In so far as it makes sense to say RNA vaccines “change your RNA”, for most of your body, it doesn’t; even where it does, it only does so temporarily.
~Max
It’s more likely that muscle cells, rather than blood cells, are the ones that absorb the mRNA. Or at least they’re the ones that use that RNA to make spike proteins. Red blood cell do not have nuclei nor the other stuff that is needed to make proteins.
Mature red blood cells have neither a nucleus or mitochondria. They may have some free-floating DNA for regulatory function but as their primary purpose is to carry oxygen and they don’t undergo mitosis they don’t really need a genome. The SARS-CoV-2 vaccine will be absorbed by cells with ACE2 receptors (a lot of cell types do) and then express an antigen that stimulates the immune system to destroy the cell (preventing viral replication) and/or attack the invading pathogen (destroying virions before they can invade cells).
Stranger
FTR, I was thinking of white blood cells, and maybe whatever cells line the bloodstream. I want to say epithelial but I don’t think that’s it.
~Max
Almost right; you’re thinking of endothelial cells (those lining blood vessels) and SARS-CoV-2 definitely attacks those. I don’t think there is any evidence that it invades leukocytes (white blood cells) although there are viruses that do, notably HIV.
Stranger
We were talking about the cells absorbing the vaccine, not the virus.
~Max