Ha! I wanted to do this too, then read your post. I finally got a chance to do it yesterday and took some pics along the way for you.
1) pop-off the lighter and ring (there's a page somewhere describing this)
2) wrap and solder the wires to the lighter accordingly (don't do like I did...tyr to keep the round cross-section, so try to have the wires angled straight away from the lighter and NOT around the lighter's sides or major difficulty going through hole. Also, orange ring needs to be installed alone first, so make sure wires aren't in the way!)
3) I put a lot of hot-glue over the connections to insulate
4) fish wires from inside towards ashtray section
5) solder wires to plugs. I didn't cut the bulky plugs off because they usually step-down the voltage to your devices....
6) wrap all wires and connections with electrical tape
7) fish wires though slit found in ashtray compartment
8) use tie-wraps to keep your wires in place (make sure this doesn't interfere with ashtray closing)
9) connect your stuff!