It's in BM's interest to make servicing a mysterious and apparently dangerous process for the home mechanic, it's a big earner for them as there's no way the profit from a few bike sales will keep the shiny showrooms open.
If you've regularly serviced your own bikes you'll realise what a doddle the GS is in comparison with anything enclosed in acres of plastic and running shims instead of simple locknuts to set the valve clearances.
'But it's got two computers' the salesman says. Yeah well they either work or they don't and while they do they require no intervention. Yes there are software upgrades, but if it aint broke...
I've just flushed and bled the brake fluid using info' from the avdrider site for the 1150..absolute doddle. Yes it's safety critical but I was careful and after doing the job I didn't test the brakes by trying to stop from 100mph into a hairpin.
It's mostly a combination of common sense and the use of collective wisdom from this and other web pages in the face of ever more complicated proceedures built into the service routines by BMW that rely increasingly on diagnostic computing, most of which is designed to speed up the job for their guys
Bottom line is it's easy to service most things on the GS, but stay in your comfort zone and take care, just like everyone that has ever serviced their own vehicles always has, or always should.