'Maintenance' covers a lot of territory. Are you asking about 'ensuring chemical balance and cleaning filters' or replacing seals, redoing bearings in the wet end, replacing pneumatic switches, etc.?
It's all doable. I have an older hot tub and have other than the fiberglass shell have worked on pretty much every component of the thing. Knew zip about tubs when we bought our current place but have gotten to know it quite well over the years.
Shock, Chlorine/bromine pucks, PH balance and if you have soft water you may need calcium, in my experience any other chemicals you can get are just weak chlorine or just useless. But it has been about 8 years since I did that for a living.
I have been maintaining one for 12 years. Started out with chlorine then switched to bromine. Alkalinity, ph, and bromine levels is all I tests for. I ususally dump the water every 4 months and give it a scrub. Inthe winter I just dump it down the sewer and do a refill without a scrub. Best thing I can recommend is to have more filter cycles to keep the water moving to continually have the chemicals dissolving into solution. I also use pool chemicals rather than spa beause they are cheeper and do the same thing.