I also installed a Garmin 182C GPS unit in my dash over the weekend. I put it in place of the compass but ran into the dilemma that the compass hole was bigger than the hole needed for the GPS. I got some white Lexan and routed the edge and mounted the gps on that. Took some pics along the way and figured I'd post them. Maybe it will benefit someone or give them an idea!
PS- I figure that I can really post whore on this one!