Yes, a halfway decent multimeter/circuit tester will do the trick. They're not expensive and will give you more information than just one of those pen-type testing probes with a lightbulb on the end. You can find them anywhere really. The reason I say that is because once you've got the harness all in and everything hooked up, you'll be able to make sure there actually IS 12 volts on wires or circuits that need a full 12 volts. I don't trust the lightbulb probe type testers for certain things like the distributer/coil, alternator/charging system. I want to know exactly how many volts is there.
The Ohm setting(s) will test whether there is continuity of a wire... an open wire or circuit, or a shorted wire or circuit. There should not be any power on the wires when checking the continuity. Obviously the DC volts setting will tell you whether you have power on a wire or circuit. You'll have to have some sort of 12volt power source on the wire or circuit in order to test whether or not it's getting power.
I hope this helps! Good luck Rob
[This message has been edited by HwyStarJoe (edited 06-28-2001).]