Hi,
There's a ton of info here on just that subject.
First thing to note, thanks to BMW's confusing labelling, you have to be careful -since you have an '81, you have an R80G/S - and the / is critical. There is also an R80GS - and it's a very different beast, made from 1988 on.
to answer your questions,
1. Nothing needs to be done to the swingarm at all. Change the oil as recommended and that's it.
2. Forks are fine as is, although they can be improved. The R80-100GS had better forks, and it's a bolt on swap. Did it myself, definitely an improvement.
The standard frame is fine, but the rear subframe is hopeless as is for overlanding. There is a ton of info on this site on that. Also see the "Our trip" link top of the left menu, and "Our bike" from there, and see what I did to my 86 G/S.
So when are you leaving?
(You do know that the trick to actually leaving is to tell
everyone you know you're leaving
and when - then it’s too embarrassing not to do it, so you have to go!)
Bognor??
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Grant Johnson
Seek, and ye shall find.
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One world, Two wheels.
www.HorizonsUnlimited.com