Merit used a couple of dozen different makes & models of monitors in the Megatouch series. On the back of the neckboard of the monitor (and sometimes on a paper sticker on the outside swingup rear door) is a label that says something like "Type xx Monitor". That tells me the make and model of the monitor that Merit used in your particular machine. You should repair the existing monitor if possible as replacement monitors are very very expensive.
Monitors from the XL series are VGA resolution and do
not need an isolation transformer.
The touchscreen glass is bonded (glued) to the front of the monitor with extremely strong glue then wrapped in special black friction tape to seal out dirt and protect the touchscreen wire harness. It can be removed, but it's very tricky. This is a very expensive piece of glass (average $250) and I recommend only professionals or persons experienced in this procedure attempt to remove the touchscreen glass. Once the touchscreen glass is off and were successful in not damaging/scratching it then you'll need to buy the re-bonding kit to attach it to a new monitor.
Megatouch games only work with two touchscreen manufacturers: Microtouch (the most common in Megatouch games) and E.L.O. (the least common and a real piece of ---steaming pile of meadow muffin---). They only work with their respective touch screen controllers. In other words a Microtouch touchscreen only works with a Microtouch controller box.
Here are Happ Controls replacement Megatouch monitors:
49-4019-00 VGA 13" Monitor Kit with ELO Touchscreen and controller $770.65
49-4022-00 VGA 13" Monitor Kit with ELO Touchscreen, no controller $579.95
49-4020-00 VGA 13" Monitor Kit with Microtouch Touchscreen and controller $848.95
49-4021-00 VGA 13" Monitor Kit with Microtouch Touchscreen, no controller $611.90
49-4023-00 VGA Monitor Kit without any touchscreen $369.35
49-0919-10 Microtouch 13" Touchscreen glass only for Merit XL $352.75
49-3068-00 E.L.O. 13" Touchscreen only for Merit Megatouch $378.00
49-4035-00 Touchscreen bonding kit $11.00
Keep in mind the above prices are from my copy of the 2001 catalog so naturally prices will have increased since then.