When you say your decks need a good service, what makes you think that? Is there anything wrong with them?
I managed to get hold of a service manual for the 1210s years ago (not sure if I still have it) but it doesn’t involve a great deal.
It’s usually resetting the zero to match the platter strobe/dots, lubricating the bearings on the motor, changing the pitch sliders, and possibly changing the leads…there was some circuit testing if I remember right, but not 100% sure.
If your pitch sliders don’t have much play/wear on them, you can get some electrical contact cleaner to spray in which can help, a little oil on the bearings and it’s job done.
Like jack, I’ve had my 1210s a long time, got them new in 95, and they still work great. I have done some work on them, but I absolutely hammered them.
If they work and you like them, why change?