This thing about porting ST games direct for Amiga remebers me the time when I had my MSX, and had to deal with direct ports of Spectrum games.... so, I had my MSX, capable of showing at least 16 colors at the same time in the screen, move 64 1-color sprites in a black background (Ok, not that useful), and playing those crap looking monocromatic games..
I never saw an Atari ST running, the only atari machine that reached Brazil was the Atari 2600.. I am discovering the Atari ST NOW, with emulation... but it seems like ST emulation is rather bad yet....
About Elite... the Wolf MK II, the Shuttle and the Transporter are in te MSX version too..., and I believe at least the Wolf MK II was in the C64 version too...
Elite PLUS on PC has nice graphics, but the gameplays isn't very good (comparing to other versions) for me, the Amiga version was the best one (Ian Bell said the NES version was the best one!, but maybe it's just because it was a hell of work to code it, and he probably was very proud of it)
I don't think there's a "guide" to get this mission on Elite, it just happens after some time playing... anyway, I'll do a quick research and see if this really true