the most important thing is transmission, make sure that sleeve is clean, if its been stored for a while you might find some ionised gunk stuck hard to quartz, if need be water down a little vinegar and use that to clean it.
while you have it apart check the hosetails for signs that they are perishing, (discoloration, powdry brittle feel), if they look good check the seals as well don't forget a little silicon lube from a pool shop will keep them good for a much longer period of time.

other then that the only thing it might need is a new bulb, if your old one has had more then 6 months of use.

they are reasonably simple devices so long as they light up and stay water tight you wont have any issues.