I was on Tricare Prime (active duty) at the beginning of my last pregnancy. I wanted to see a nurse-midwife and because I am not allowed to change from Prime as active duty I had to drive all the way to Milwaukee to see someone.
If you are a spouse you can elect to use Tricare Standard instead of prime which will allow you to see any provider who is credentialed by Tricare (it seems most providers are credentialed, it's generally anyone who accepts Medicare). You can also use the point of service option to see anyone you want but it results in out of pocket charges.
On standard even if your provider opts not to contract with Tricare you can pay up front and get reimbursed by Tricare- that's what I did with my kids because I wasn't willing to see any of the local Tricare contracted physicians, they were awful.
There is a maximum distance you cannot be forced to drive beyond to see your provider- I want to say it is no greater than 45 miles or one hour. Not positive on that and it is very hard to get them to agree to transfer you. I was forced to wait 8 months for a referral to a specialist because they were trying to send me to St Louis (at my own cost) because there was no one in the local area. So frustrating!
There is a Tricare office at Great Lakes and one person who works there named Christina was always very helpful to me. Calling Tricare is generally worthless because you will get a different answer every time you call- be sure to write down the name and the date/time you talked to someone. I made a congressional complaint and Tricare actually lied about the number of time and dates I had called- luckily I kept a log of my calls. They ultimately apologized.
Good luck- I actually left active duty for a civilian career about 1.5 years ago and a large part of my deciding factor was how terrible my health care was on Tricare in this area. If I can be of help in any way please send me a message.