I just replaced my EGT today. There are about 7 screws that hold the instrument panel in place. Then a pair of nuts that hold the gauge in place. It tucks in behind a holder that holds most of the other instruments in place. And there is a black plastic ring that block out stray light. The original gauge was not much. You can replace it with a modern much better instrument for a couple of hundred bucks. I went with 2 1/16" Auto Meter. Hardest part of the refit was running the cable from the probe back to the instrument panel.
2000 28' Classic TT
1994 30' Land Yacht M/H