I've done it a few times before. The bezel is an aluminum ring crimped around the edge to secure it to the white plastic body.
From the back side, take a very small screwdriver and get between the edge of the bezel and the white plastic body of the gage.
Twist the screwdriver to bend the crimped edge up and away from the white body. Work your way all the way around in tiny increments, eventually the entire lip will be 90* to the face of the gage and the bezel and glass will simply come off the body.
To put it back I put the gage face down on a table with a cloth to prevent scratching the black bezel.
Use a very small hammer to lightly tap the lifted bezel edge back down, rolling the edge you lifted back down again, working your way around the gage.
You will now have it back together and just a little satin black paint or black sharpie will tough up the small nick marks ( if you even care ) on the back side where the screwdriver scraped off the black anodizing, not that you can see it once installed anyway!