After almost 9 years at sea, we've had to
rebuild our capstan twice. Both times, the
seals and bearings on the shaft needed replacing (water seepage coming into the boat). The
gearbox has been serviced twice (water ingress - not serious, but since we were servicing the rest....)
We have a wireless
remote (cheap jeep
windlass remote) that only seems to last for a year or two. We always carry a couple of spares. Finally you should carry a spare solenoid. They can be difficult to source if you are in non-civilized places.
But the first thing you should do is take your windlass apart and put it back together again. That way you know how to do it. This past time, getting our capstan out was a bear and required the use of an shaft puller. The one I have for my maxprop wouldn't fit. Luckily we were on
Martinique and the the local
chandlery had one.