I too had the Amiga disk drives inside and out, but found it mostly an introduction on how NOT to code on Amiga.
As for 68000 programming, i'm entirely self taught. Never once picked up a 68000 manual for any machine.
I learnt by using Action Replay MK1 and basically pissing around with its in built assembler and stepping through programs to figure out how the code worked.
Other than a couple of pointers early on about how the Amiga makes up its screen, the rest was learnt by looking at other peoples code.
The system friendly stuff was by looking at example code.
Its part of the reason I still do Amiga stuff, its a lot of information i've learnt and I don't feel like losing it.