Its a long process
T-topflyer,
Send me your Email via PM and I will send you a MS Word document I put together to get "Gold Wing" folks transfered into the Air Force Reserves. I would assume the process is similar for the Guard.
I would basically agree with pony251 on everything - especially the AF physical. I transfered over a few years back from AD Marines to the AFRES and it took nearly 8 months w/ all the paperwork (start-to-finish). There are also a lot of idiosyncracies (spelling?) depending on your situation (eg: Helo guy, passed over once/twice?, time in service, etc). Your best bet is to contact an AF reserve (assuming your going into the reserves) recruiter, and read over the MS Word document I have put together (well almost done putting together). That should answer almost all your questions.
By the way, its never to early to start the process. We are currently trying to "gain" a Marine C130 pilot and it has been over 11 months since the paperwork started. Looks like it will be a 13 month process when its all done.
Good Luck,
AArider