Many a Compass have the heel guage on them but my Plastimo does not. I got a seperate inclinometer that measures up to 50 degrees of heel each side, (I have never gone beyond 40) which I mounted right in the center of the companionway sliding hatch under the handle. I can see it clearly and quite like being able to see how many degrees of heel the boat can take and at which point it really hardens up.
The hole that is left from removal of the old unit should be a standard size that a new one will fit, just measure the diameter and then check the instructions on the new one for hole cut size. A seperate clinometer is nice too.