My first question about your favourite mare is how torn up you would be if you lost her in the course of breeding/gestation/foaling. Do you "need" her as a riding horse?
Most pregnancies and foaling go fairly smoothly, but when things to wrong then can go south very quickly. There is always a risk that you aren't getting your mare (or a foal, for that matter) back at the end of the day.
When I used to work at a breeding farm we foaled out 30-40 mares a year and it was not uncommon to lose 1 or 2 a year. Some years were super smooth, but sometimes no matter what you do things come apart at the seams. I remember one morning with a mare that had just foaled bleeding to death due to a ruptured uterine artery in one stall with a maiden mare trying to savage her foal in the stall across the hall, with people and the vet rushing back and forth trying to tranq and restrain one and stop the bleeding on the other and get colostrum to the babies, etc etc. It isn't always how it looks in the books.
As Peter, Paul, and Mary say, a dragon lives forever.
I would contact your 'very good repo vet' and have a very long discussion with him/her about how to proceed. If that is the person you have chosen to work with, they should be able to provide every detail you need plus answer all of your questions and guide you through the entire process.
I am breeding my first this year, and I did address these questions with my vet. I would be heartbroken if I lost the mare, but having been a pro in a past life, can ride anything just about, so she's not irreplaceable.
I will say that I do have her insured out the nose for mortality and major medical.
One of the best breeding resources I know is equine-reproduction.com. There you will find many articles on breeding topics. There is also a Facebook group and a yahoo list moderated by Jos and Kathy, of equine-reproduction. Just about any question you have can be answered there.