changing an airbag slip ring

my airbag light is on all the time the ignition is on.
Took it to vw and they said the fault was the slip ring in the driver
side airbag. they want £90 for the part and £97 to fit it
I've read on some sites that the problem can sometimes be solved by
lubricating the ring or resitting it - anyone know somewhere that has
clear instructions on how to do this?
I replaced the combination switch a few months agon and the airbag
light problem started about a month or so after that
is the slip ring on the back of the steering wheel? the, what looks
like, a solid copper/brass ring which connects to a connector on the
steering column?

thanks for any help

passat 2 auto m reg