I'm installing three OTRATTW switches on my '04. I already have them mounted and wired except for the number 6 pin that connects to the dimmer wire. I read somewhere that it's the blue with red stripe wire that connects to the dimmer ****. Is this the right wire and how can I tap it without cutting the existing wire off the ****? And where are some good ground locations under the dash? I couldn't find one so I just plugged the ground wire into the negative terminal on the battery for now...

 

That wire is the correct one... You could also tap the wire in the radio plug. It's the same color. If you don't want to separate the wire, you can use and in-line splice.

Plenty of places to ground to... Just pick something that will keep the wire out of the way. I used the bottom of the dash along the area where your shins normally are.