There are so many cabinet variations out there, all of them a little different. Even among Dig Dug cabs. However, I've pulled apart and restored a lot of cabs
You probably won't see any screw etc at the front of the monitor/glass. This will be by deliberate design, because it looks better. What a lot of cabs do is slide the glass up/over the monitor from the bottom, secured by either:
- a metal bracket to hold it in; or
- the top part of the control panel holds the glass, and the CP comes off or swings up on a hinge
If the glass is held down by control panel, get a light and have a look underneath the control panel. Look for 2 clips (1 each side) that hold the CP firmly in position. Release the clips, but be aware they have a bit of spring tension in them and may open very suddenly.