K75 help

I have recently aquired a 1987 K75 S. Apperantly in late 1987 they
added a brass ring to the top of the tubes in the front suspension.
What is their function? Also, can anyone direct me to a step by step
instruction on how to change the fork seals on this bike? I have tried
many K bike resources with not too much luck. I am sooo loving this
bike

Dave