With respect to the FM3a screens, the information about exposure compensation couldn't be farther from the truth. I've owned a couple FM2's (and an FE2) that I installed the K3 screen from an FM3a into. The meter did not change its reading after changing the screens. I currently have the stock K2 screen in my FM2n, but I do plan to install a K3 into it when I have some more cash.
Anyway, welcome back to the F3 and FE2 world. If you're in need of a flash that'll work with both, but the AS-17 adapter seems hard to come by or too expensive, check out the SB-16... Just make sure you have both modules for it. It's a bit like a more versatile and TTL compatible Vivitar 285HV. The 300f4.5 is a pretty nice lens, even in the non-ED/EDIF version. Owned a couple of the older chrome barrel Nikkor-H versions. The only thing I didn't care for was the close focusing ability and the weight. Found that the 300f4.5 EDIF was quite a bit lighter, and focused closer. With a couple extension tubes, that lens actually became a fairly decent macro lens.