Just found this thread and would love to see an update on your progress with Judge Dredd. I am in the midst of my own Judge Dredd shop job. You've inspired me to do more than I had planned and so I started to completely strip the underside of the playfield last night so that I can really clean and refurbish every part.
I have seen that on many Judge Dredd's the large inserts near the JUDGE targets seem to always be raised and have the clear coat cracked around their edges. Was yours like that? The cracking on mine is bad enough to make me worry that it'll get chewed up there with lots of gameplay and so I am now seriously contemplating having it professionally clear coated. I'll lower all of the inserts beforehand and have purchased a 12" deep throat c-clamp just for that job.
You have also inspired me to have a go at regraining my stainless ball guides. I don't have the equipment so will have to go out and get some - this machine is starting to get very expensive