IANAD, but I recently had a hysterectomy and this is what I know from my research.
When the uterus is removed, it is detached from the ligaments that suspend it in the abdomen and the cervix is detached from the top of the vaginal canal. The canal is then attached to the ligaments. In my surgery, it was also sewn to the rear peritoneum (I don’t know if that happens with all surgeries, but I do know it happened with mine).
This is done to prevent the vaginal canal from collapsing in on itself and to keep other abdominal organs (bladder, intestines, rectum) in their proper places. Hysterectomy can be a risk factor for the prolapse of these organs in later life, so it’s important to keep your weight down, not smoke and stay in decent shape to reduce the risk as you age.
The vaginal canal (now called the vaginal cuff) is also sewn shut. If it weren’t it would be open to the abdomen, which would be a Bad Thing. It’s very important the cuff heal together properly. Women who are very overweight, smoke, are diabetic or have immune system problems heal more slowly and need to be more closely monitored by their doctors.
A thankfully uncommon negative outcome of hysterectomy is known as vaginal cuff dehiscence. This is where the top of the cuff is either split open (most commonly due to too early or too enthusiatic sex) or comes open spontaneously due to poor healing. This can cause severe pain, bleeding, loss of abdominal fluid through the vaginal canal and even evisceration - the small intestine can collapse into the vaginal canal. If the intestine loses its blood supply that can result in an emergency bowel resection, so it is very important to listen to your doctor and not try to have sex or do strenuous things before you are cleared to do so. Even then, it is important to use common sense. While it is typical to be cleared for full activity 6 to 8 weeks after surgery, if you don’t feel 100% mentally and physically ready, listen to your body and don’t let anyone pressure you into doing more than you are comfortable with doing (I know I wasn’t ready for everything even after being cleared).
For traditional abdominal or vaginal hysterectomies, the incidence of dehiscence is typically around 1 percent, but for laparoscopic or robotic surgery it is higher - 4 to 5 percent. No one is really sure why at this point - it’s been speculated that it’s either due to the type of scalpel used to separate the cervix from the vaginal canal (it generates heat which may affect healing) or with the method of stitching or type of suture material used in these surgeries to sew the cuff shut.
The surgeon wbo did my operation published a paper wherein he and his colleagues reviewed laparoscopic surgeries done at their hospital for several years and saw that surgeries in which barbed sutures were used to close the cuff resulted in better outcomes (zero incidence of dehiscence in their review) than with other types of sutures, so they only use that type of suture material now. A study is currently being conducted at Brigham Young to see if they have the same results.
As for the OP’s question, things should be cleaner now than ever before - no blood or cervical mucus, so it’s actually better. And yes, the vaginal canal is self-lubricating and as long as there’s estrogen to help the process along, no worries there. You don’t want to do anything to dry that out.