To get the full feel of a glory-hole at an incall, it would be best in a duo situation. where there are 2 girls on the other side, and you're not really sure who's sucking you off at any given time. The whole anonymity/NSA thing...
As for construction - just ask the Home Depot guys about putting a wooden 'patch' on the door for a hole - and that you don't want to replace the whole door. There are a variety of options, and simply hinge them instead of installing them permanently; or make them easily removed.