I'm nearly done with the Star Wars Episode I pinball. I have:
Replaced alll lights with LEDs
Rebuilt the flippers
Cleaned this... unknown glop from the playfield and even under the playfield. Seriously it was some dark sticky tar that was adhering to anywhere the balll was
Replaced the balls
Added playfield spotlights
Replaced the T molding on the outside trim
Removed the fluorescent light and replaced it with a USB LED strip
Replaced all playfield posts
Replaced all playfield and flipper rubber
Retuned the pop bumper switches to 1/16 of an inch to make them fire more consistently
Cleaned and repaired some side art damage
This game was what is called a reimport. 50% of Williams' business at the time was based on exporting the games to Europe. This particular game went to Norway. Where Williams messed up was exporting the game to countries that didn't have the movie playing yet and wouldn't be playing it for MONTHS. So, yes, the property was kinda bad, but people seriously had no idea who these characters were in a movie that was months away.
If you've never seen a Pinball 2000 game, it uses what's called a Pepper's Ghost illusion where a CRT monitor is mounted in the backbox and the image is reflected onto a mirrored playfield glass, giving the illusion that the playfield is changing and reacting to what is being displayed. It is a convincing illusion and makes the game very interactive.
Anyway when I picked it up the monitor image was awful. Greys were invisible and dark colors were muddy. I was convinced that I would have to replace it which is a little out of my league - I can work on pinball games but CRTs are explody bombs that can act like capacitors and can kill you if you touch the wrong part of the exposed innards.
As an example:

The green starburst should be bright and cover the playfield. Adding LED lights would just make it worse. I was able to adjust the gain from the neckboard of the CRT carefully and get the picture to be a lot better but at that point I had no where else to go with the picture:

It looks good but you can see through the image quite a bit and I had no more adjustments left. Any gain and I would get pink diagonal flyback lines across the screen from over volting the neck.
As it turns out, there is a design flaw from Williams that needs fixed - the voltage coming from the CGA video card is about 1/3 where it needs to be to give the CRT a good signal. The picture may have never looked good. I could replace the CRT with an LED/LCD monitor but this takes some serious retrofitting and also loses some of the 3D effect. A company called Ultimarc makes an amplifier addion though, that can be added to many arcade games and it works in this case - it boosts the signal from a VGA/CGA source and give the CRT the correct RGB values to a clear picture.
One Ultimarc amp later:

And it looks much, much better. I made a new wiring harness with Molex trifurcon connectors - my first time doing this and I'll never do it differently. Now the picture looks like this:

And while it may not look like much, there is a big difference. The star field around the inset video frame is actually visible and much less of the rear plastics and playfield is visible through the image. The white of the sky is bright with plenty of saturation, and the LED lights don't blow out the reflection. Also, I could turn the gain WAY down as well as the manual brightness and contrast controls - I have someplace I can adjust the picture to in the future! Really happy with how this turned out.