I have a NGG myself.
By looking at the pics you posted, the playfield seems in good condition beside the slam ramp wear that is pretty usual on a NGG. They sell a decal for that or at least used too, it was done by Treasure Cove. I don't know if they still produce it though. The inserts are only an aesthetic default and at that price should not be a deal breaker.
The mechanisms on this pin to look for are the gofers themselves and the spinning wheel. Concerning the gofers the usual trouble and the one I experienced personally are related to the optos located in the gophers and the rods that make them go up or down, the culprit in that later case lies in adjusting the rollpins located in the rod and replacing them. The optos and the rollpins can be fixed easily and the costs associated to those issues are minimal. I personally do not know if fixing the wheel is a cheap and easy fix, but I think the parts are still available if the wheel is not functional.
If the machine plays great, the price seem to be really good. It's funny, it was my first pin that I bought back in 2012 for exactly 2500$ (cad) and that got me into pinball!