Hi Denice and welcome!
You ask about the normal size of a uterus ... here is a quote from the book "Fibroids: The Complete Guide to Taking Carge of Your Physical, Emotional, and Sexual Well-Being" by Johanna Skilling.
"The average uterus is 2 to 4 inches long, 1.5 to 2.5 inches wide, and 1 inch thick; it weighs about one-sixth of a pound or 50 grams, if you're metrically inclined. If you've ever been pregnant, your uterus may be on the larger end of those dimensions. Now remember, that's the size without fibroids, adenomyosis, polyps, or pregnancy..."
I'm not sure about the 11 cm figure that your gyn mentioned ...
Yes, in almost all cases where a hyst is performed vaginally the cervix is removed. If you choose to have an abdominal incision or a totally laparoscopic hyst you can keep your cervix (depending, of course, on your gyn's recommendations about the condition of your cervix, etc.)
As for rectocele and cystocele ... these are prolapse issues (rectum and bladder) that we see a lot of here at Hystersisters. I didn't have any prolapse problems so can't speak from personal experience, but we have some great resources listed at the top of this forum including some wonderful resources for prolapse. Here is the link to the list of resources ... be sure to scroll down to find the ones about prolapse
A second opinion is ALWAYS a good idea when you are considering major surgery. I encourage you to get at least one other opinion before making a final decision about surgery or other options. We'll do our best to provide support whatever you decide.