shimano nexus hub gears

[Hugo a Gogo]

OK, not a lycra tour de france subject, or a downhill broken bones story

just a plain old town shopper bike with a 3 speed nexus with back-pedal brake
do these things just wear out or can they be serviced in any way?

I just realised my bike is about 10 years old and has done a few miles, never had a bike that long, and it's getting noticeably crapper changing gears and holding gears on slopes or pulling a trailer

was thinking about just getting a complete wheel for it, any thoughts?