Area where the VUK delivers the ball to the upper mini playfield. Best case there is a metal protector/cliffy there or the pf will be damaged.
Check condition of all ramps, they can be bought but there are 7? in total and it will be very expensive if replacing all. Look especially close at the whirlpool ramp (where the ball goes around in circles) and the two ramp entrances behind the green standup targets (ramp plastics get smashed by the ball).
I would also check that bigfoot works properly (turns head and divert balls).
Check condition of all mountain plastics, can be bought but not colored exactly the same as originals and also rather expensive.
Check playfield in front of "lost mine" kickout as that area often get really worn and missing paint.
Check topper works properly. The waterfall should look like the water is flowing when working correctly. A working original topper is unobtanium as spare part so if you find a game with a working one it adds quite a bit to the pin value. If the topper is missing then the price should be lower, topper is an iconic piece that shows the game name (game title is not present on the translite).