If your A4000 has 3.1 roms(If not i would get that as the first upgrade), i would recommend OS3.9 it's what i use on my A2000 and A4000 and that has a lot of drivers for the Amiga (proving you use the OS3.5 ones on the OS3.9 CD).
Your not alone in having to relearn lots of stuff.... :-)
But this is the best place to relearn, everyones really helpful here(I know people have helped me heaps since i got back to Amiga's).
Anyway enjoy... :-D
