Re: install in my friends car
Make sure you use some kind of rubber or plastic grommet whenever you run a power wire through a piece of sheet metal. The previous post mentioned removing a plug in the firewall and running the wire through the hole. This is usually the best method. You can even cut a small slit in the plug, put some Astroglide (this was its original design purpose) on the wire and run it through the slit you made, using the plug as the grommet. Using an existing hole is almost always better than dirlling a new one because there is no way to drill into something important if you don't drill at all.
Don't be afraid to remove seats, carpet and trim panels to make running the wires as easy and neat as possible. If you have everything ready to go, you can basically take out the interior, run all the wire, and put the interior back in in about an hour.
Artificial Intelligence is no match for Natural Stupidity.
Never underestimate the power of stupid people in large numbers.
Life's tough...it's even tougher when you're stupid.