Usually you drain the oil out of the drain plug and then find out what kind of your oil. It takes an you fill it up until it starts overflowing, but I would ask the BMW dealership to make sure
Or visit a site called Carl Salter.com and get a manual for free ,thats what I doo it's an excellent site with no catches.you can even save the pdf file to your pc.
The ABS lights can come on for a number of reasons, not least of which could be the condition of the battery, although I can't think why it should happen after travelling 500 metres. You may just get away with resetting the ABS system, the attcahed link shows how ou can do this ith ABS1 and ABS2, what harm could you possibly do? (answer; plenty, but the narator seems to know what he's talking about)
BMW Motorcycle ABS II Reset
On a 1997 and 1998 BMW K1200RS gearbox oil should be inspected each 20,000km. Changing the oil is very easy, and shouldn't take more than a few minutes as it down't look like the side panels need to be removed.
As for the lever sticking at 3rd gear, try lubricating the selector. If it is a more serious problem then you may need to rebuild your gearbox. However I would put up with the problem for as long as you can.