It will be costly if you go to a good tech. The good news is that you can all DIY if you're handy with tools. I did buy a junk Rhodes 54 some years ago for cheap. The thing was all clacky and rusty inside. No sound at the jack output. I did buy about $150 of parts online and went at it after some reading. It took me about two full days to dismantle the thing entirely, clean everything, put some new felt were it was full of mold and resolder some pickups. Once all done, the thing was as good as new.... You need to check first if the wooden keys aren't all bent. If that's the case it will be much more difficult to get the thing up to par.