I've never seen the interior of a first gen, but I know in the second gen there's a panel with map lights (where the sunroof controls go if you have one) and i'm pretty sure you can run the power from there. also, if you're lazy, Nissan sells and installs factory mirrors with the compass.
Thanks Godzildo. You are right the dealer will do it and what I found was this: From any other parts dealer (mail order) the compass/mirror starts at $225-250. Then you have to install it yourself. The dealer on the other hand has the compass/mirror for $189 and the compass/temp/mirror for $209! So the part is already less expensive through the dealer. Then my local dealer quoted about $100 for the install if they have to run a harness. For $289, ya might as well have the dealer do it!!
Well, GPS is a bit of a step from a compass. My grandma's cadillac has a mirror with all that OnStar crap, and it has a compass/temp guage. It's pretty tight, you can see what direction you're headed.....that and I just like all the gadgets I can get. But if you want something with detailed directions and junk, go with a GPS unit.