[ben]

How mechanically minded are you?

I have worked on a few Sonys of this era, and because they have one motor and one control lever, there are a number of levers and rods and linkages used to distribute the motor drive motion and select the functions. The grease will likely have turned to treacle after 45 years, so considerable disassembly will be needed to clean it all off and reapply. No matter what the seller says, this will be necessary to get it working reliably. It is not too bad if you have an aptitude for such work, take it slowly and are methodical, but expect to spend 3-4 hours minimum.

As Glyn says, the electronics should be fine. Some contact spray on the pots might well be all that's needed.

edit: to give you an idea, I attach a doc with images of the sticky linkages!