First job I would say is clean the entire machine , pull the cards , hoover up dust , wipe down everything until its spotless ,examine everything as you go for obvious faults , loose linkages nuts bolts and screws etc . Double check your capstan lube is compatible with whats already in there . Good advice from Abbey and Gold , follow the long game service procedure in the manual , once you have taken care of all that , then consider applying power with due caution .
Bearings in the rollers/transport might benefit from a small drop of light machine oil , one drop at a time , work it in until they rotate freely . With a bit of luck and work the mechanical side will come right , now you can start to methodically work through the electronics .