I am joining this thread rather late, so, please excuse me if I repeat anything that has been said before.
Let me start by saying that I think this is a wonderful idea.
Referring back to an earlier post from DarrenOP I believe, I have to say that I agree with the concept that if you are going to embark on this you should do so with your end goal in mind. If the goal is to learn C++, for example, you might want to start with C++. The ramp-up time might be a bit difficult, but, in the end you will be better for it, in my very humble opinion.
Also, if I may suggest this, you might want to immediately look into getting a copy of the Amiga Rom Kernel Manual - Libraries. This RKM is very well written, with lots of example code and explanations. I think that it also would be helpful in the sense that the Libraries RKM has information in it pertaining to the kind of "instant gratification" items that a beginner might want right away. Such as opening windows and the like. Also, since the Amiga is mostly based in the C space, you can pick up any decent ANSI C book for a desk reference.
If it would be helpful, I would be glad to assist in any way that I can. I am a senior software developer and also do some work with architecture and design. All that I ask is that my involvement be strictly in the scope of the Amiga. I spend my days battling with Microsoft's brain dead API's and I would rather spend my off time working on a platform that was done right ther first time.
Thanks,
Mike