Get some plastic cleaner/polisher for the playfield. Take a good look at the balls if they are dented, rusted, or damaged in any way replace them the damaged balls will act like sandpaper on the playfield. Get used to soldering. Get a manual for the pin if it doesn't come with one. Find out what lights it uses and buy a box they tend to burn out. Umm that’s all I can think of off the top of my head.

Hope that helps
Later
Rob