well, the mac classic GUI is fully documented and easily usable. You can serch out the volume Inside the Macintosh on Apple.com, they have all the API calls. There are also some very good (albiet old) books by Dave Marc like C on the Macintosh and Inside the Macintosh Tollbox. These are geard to the Old THINK C compiler.
If you want a free compiler for the Macintosh you can downlowad a compy of MPW from apple. Mac Programmers Workshop. It's a fully fetured programming environment.
Thw 7500 is a nice old machine, have one myself. But today it's a dinosaur, at least for modern stuff. You can't run OSX on it, but you can do photoshop work with it.
What sort of programming are you interested in?
P.s. You may also want to familiarize yourself with Apples operating system architecture. Learn about the diffrent layers like QuickDraw, the Resource Manager etc.
The Mac API is alot more elegant and simpler than Win32 (naturaly), but coming from that world you may find yourself lost at first.
[ February 26, 2003: Message edited by: psyjax: plain 'ol psyjax ]