Buying a pinball off eBay these days is like chook lotto.

As Rob said, build up the area around the hole before fitting a cliffy.

The monitor probably needs to be degaussed. These color distortions can be caused when moving the machine or when placing it next to items with a magnetic field. The motor in my Garage door does the same thing with arcade monitors. Could be a simple case of leaving it be as the chassis may degauss the tube over time anyway.