Learning to program is like learning anything else in life - looking at the 'big picture' can be a little daunting.
It's no different from learning guitar - you can look at Eric Clapton or Mason Williams and say 'oh...I'll never be able to do that' and give up. Or you can break it down into tiny steps and take one of them at a time.
I'd programmed on several machines before the Amiga, and the more I watched and read, the more the big picture confused me.
I was going over some really old comp mags one day and I read an old interview with.. I think it was Richard Garriot (Ultima) and he said of learning to program 'If you want to make something - just make it - and everything you need to know you'll learn along the way'.
I ordered Devpac III the next day. I was never a 'star coder' - but I enjoyed my own little projects, and helping out my mates with the odd scrolly intro here and there.
Now - 11 years since I had my last Amiga, I'm starting again from scratch. 1 week of work and I already have caught up a lot. It's so much EASIER now that I'm older and have the resources of the internet at my fingers... need some info on a register? Google away and a minute later you have all the info you want! and more!
If you want to make something like this - just do it, and ask questions, and look stuff up, and everything you need to know you'll learn along the way.
As for me - it's an interesting project, but I have one of my own atm..... and I never really played Guitar Hero (not my kind of game...) so anything I would do would look like just an experiment..... not the game you want.
I will, however, give whatever ideas and advice on a technical level that I can.