I don't know if you can "find it all", but you may be able to build what you can't find. This is a small community, tiny by comparison to those that run E30s or Civics, but there's not a lot of BS and those that compete (see track talk) are serious about what they do. For better or worse that does mean that, while you will get some good advice here, you are unlikely to find information on how to duplicate the setup of a championship winning car in whatever class you run or build a fast setup easily from off the shelf parts.
Aftermarket is virtually nonexistent, there is little plug and play, but as others have mentioned, 10, 12, 14 and 17mm sockets will dismantle 90% of the car. The car does have some limitations--it does better for it's class in power to weight than it does making grip, so it does better in road racing and rally than in autocross, where I compete with one anyway

It is camber challenged, and yes you will be into the gearbox a lot. What's specific to the GT is truly rare, but you can find it here if you have some patience; the parts that are shared with Geo Metros are easier to come by, though they are getting harder to find in salvage yards.
It's a great car to learn in because it is inherently better balanced than most FWD cars, you can steer it with your feet, yet it won't bite you if you screw up. The engine is quite durable, as good as a Honda or better, but the chassis, to put it in the best possible light, is not overbuilt. It's light, but easy to twist, pull apart, or mangle, so brace it up, seam weld it if you are allowed, etc...
This guy is kind of our resident road racing guru:
http://teamswift.net/viewtopic.php?f=24&t=35424And, though it may be less relevant to what you're doing, here's my autocross thread:
http://teamswift.net/viewtopic.php?f=24&t=53180I am less a fount of knowledge, but maybe you can learn from my mistakes

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