But as you can see, it is possible to get the job done.The first tool you'll need is something that you can pry the folded trim up from the gauge. I took a straight rod and used my die grinder with a flat cutting disc to cut a slice into a rod leaving the end thin so it would be able to get under the trim ring. You have to look at the pic. It's too hard to explain how to make it. Leaving the ends sharp. You'll be able to pry up on the ring. Just keep twisting the tool working it around the gauge like a can opener. Once you get about half way. Make sure you don't let it fall off and break the lens.
Now you can clean up the lens. Paint your needle
or whatever else needs done. When you clean your lens. Don't just use anything on it. use a good non-streak cleaner and a good cloth for cleaning glass. Like you would on your eyeglasses. The first time I cleaned my lenses, I used a microfiber towel. It left behind some streak. Check the fit of the gauge in the new trim ring. If it's really tight. (This will be dealing with the large gauges.) Take some 180 grit sandpaper and hold the gauge or glass retainer and slightly sand around the item making it slightly smaller. This will make it easier to get the new trim ring on.
Place something soft like a microfiber towel on the table so you don't scratch your new trim rings or lens. You'll want to put the lens retainer back in the gauge. Place your lens inside the retainer and add your new trim ring. Hold it all together and place it on the microfiber towel. "Make sure the lens stays in the glass retainer"
I made a mistake and didn't make sure the lens stayed in the black glass retainer and the lens broke when I pushed down to pry the trim ring down. What happened was; you have to hold down on the gauge pretty good and not let it come out of the trim ring. It's is going to want to lift out. If it does. Just make sure the lens is in the glass retainer before prying down. I pried the ring down on all four corners and thought that would be sufficient. You'll want to pry in all four corners and split that. Pry again. Then go back and work the first pries down until it is all pried down. I let the glass come out when the gauge lifted. I pried. It broke. 
I used a long flat tip punch to bend the trim ring over. Here's some pic's and good luck!
Finished item:
