Assuming that you have a mechanical gauge, the only wires you have to connect are to power the bulb. You can splice/butt connect the live wire to the back of your euro switch. Its the leftmost top position on your switch. The other wire is just a ground. This will allow the gauge to dim with the rest of your interior lighting. Its a pretty easy install.
Sweet, I have the same setup. Heres an old pic of my interior:
Also, don't cut the stock hose in the engine bay. Buy your T connector and small piece of tubing and use that to connect your line to the manifold thing (not sure of the technical term). You are going to want the option of returning it to stock if you need to.
[ February 06, 2004: Message edited by: RafCarre12 ]