Well easiest thing to do is lift out the cup holder plastic which will give you full view in to the dog house. Also can remove CD player and radio if necessary for more visibility. Once you have it open to view you will see there are lots of options. I can't say what the best path is to run wires in to the engine compartment but for my CB antenna mounted on my rear bumper I just ran the cable down through where the AC hoses come in. They are wrapped in a "putty" that can be molded to allow additional cables through. I'm rambling but hopefully this gives a bit of help.
I would imagine the GPS cable will be real thin and no problem to work with. CB antenna straight through the bottom might work easily as well. Not sure about light wires.
2001 H1 Opentop
Former 03 H2 Adventure Series
http://homepage.mac.com/babiak1/