I own a three month old puppy and I’ve found that when it comes to asking questions about health issues about puppies, all my friends have different answers… that’s why I’m putting this in the IMHO arena opposed to GQ.
She weighs a little over ten pounds and is healthy as can be. I know the inevitable is coming- I have to get her fixed…
What is the appropriate age a puppy should be so that they have developed enough to handle being fixed? How early is too early?
Also, how much should I expect to pay for the surgery? What have you paid (If you’ve gone through it.)
Any other advice?
You really should ask your vet these things… and with a pup who is already 3 months, you should have a vet by now!
That being said, how early the surgery is done depends on the vet. It CAN be done around 8 weeks, but vets usually like to wait a little longer. All vets should be happy doing it by 6 months, which is about the first time they go into heat. I try to schedule it earlier, as my first pup went into heat the week before she was scheduled for surgery.
Prices will be different everywhere, so I can’t really help you for that.
She is probably old enough now but I agree that a vet would be able to know for sure.
I have always used low cost vet assistance. Back when I had my girl fixed I went through Friends of Animals. It looks like they are charging $90 for a female dog.
There are cheaper assistance programs. I would google for places in your area. I know here I recently looked for a friend of mine what the price is for a low cost program I used for my cats and it was $50 for a female dog with an added discount of $10 for shots which is a great deal.
I would also get her to puppy training classes. It will make both of you happier in the long run to have a well trained dog and a well trained owner 
Why or why don’t people realize when they post about their pets that pictures are a requirement. Geeeez 
Six months is about right. Depending on the breed, you may want to do it earlier. My vet charges more for larger animals so if you have a labrador it might be cheaper to do it earlier. Our 7 month old 80 lb lab cost about $200 to spay.
Our dog was spayed at six months; before any episode of heat. Also “puppy school” was loads of fun for us, and the puppy, and very useful.
Pictures, please.