Good question. I don't have any issues at this time, just doing oil changes and lubes. She's running great. I don't want to drive into the Ford dealership when something goes wrong, and I don't know anyone who works on vintage.
I have a friend who runs a shop called Krawltex. They mostly do off-road stuff, but the owner (my friend) is a Mustang aficionado and I'm sure he could handle anything you need done to your car (outside of body work). The shop is in South Austin, though. If you do call, ask for Cameron, and you can drop my name as a reference.
That is such an easy car to work on yourself. My first car was a '66 Mustang Coupe and, with no prior car knowledge, I changed the head gasket, starter, alternator, coil, brakes, shocks, fuel filter, rebuilt the carburator, and installed a stereo. Just spend $15 and get a repair manual.