If you are getting both does from the same breeder, ask about doing a breed back. We allow our clients to bring to does back for breeding when they only have goats from our farm and are not exposed to any other livestock. They do need to pay a fee for this. We generally have enough genetic diversity so it all works out. Sometimes there is a little line breeding but no sibs, mother son, etc.
If you are going to get a buck, get 2 intact bucks instead of 1 buck 1 wether. Make sure they aren't closely related if you don't want to inbreed. That way, you already have a buck with different genetics to breed back to.
Be careful when taking does offsite to get bred, it is a fantastic way to bring disease into your herd. If you do, make sure they are tested for CAE at least!
Some sell their buck every year after they use him, personally I don't like it and only sell to people who intend to keep the buck. I put a lot of time, money, and love into my animals and I don't want one of my bucks being sold on Craigslist over and over. I will put them in the freezer before that ever happens. Mine are very much like dogs and that isn't the life I want for them.
Some vets offer AI service as well as some goat breeders. Ask around when you go to the spring show!
My goat does fine without a buddy, but not so fine with other intact bucks when they are in rut; every goat can be different. When I used to have 6 goats I let my buck run with the does as soon as I knew they were all bred since I did them all around the same time. I would then separate him back out during kidding and milking but his pen shared a fence line. I don't do that anymore, I now have three bucks and three breeds.
You don't have to worry about breeding to the sire of the offspring if you don't keep any offspring. HA HA, like that would work, right?
I went from 3 goats to 40 goats in 7 years...be very careful...be very very careful