Hmmm... I'm not at all trying to steer you away from a CustoMac, so don't take anything I say in that light. As I said, I am also still a beginner at making CustoMacs. I have only built the one, but learned quite a bit about that specific configuration.
By "tinker," I do mean willing to a) research issues you come across before asking about them (reasonably anyway), b) trying fixes that apply to your situations, c) having patience when things don't go quite right, etc. The bottom line is, the MacOS is highly tailored to specific hardware and we're attempting to get it running on (sometimes) non-specific hardware - so you'll have to be able to make changes that accommodate such. You can get hardware that is more compatible with the MacOS as-written, OOB if you prefer, and reduce your need to tinker.
As for programming languages, I'd suggest C. It is the foundation for most everything you'll do on a Mac - from Cocoa to the MacIASL compiler. Understanding that will help you make necessary edits. If you do HTML, you might do some Javascript, which is similar enough to at least get you going.
Otherwise, if you have OS skills, can work in a command line/terminal, and are somewhat comfortable with Unix, you'll be OK. This board is awesome for providing help (as long as you are very specific about what you need). RehabMan doesn't really bite, though he sounds gruff...
(just kidding RehabMan!)