Dont ever, for the sake of your car, and your wallet, go to a place like best buy to have an alarm installed.
Unless of course you want 10 ft of extra wire shoved up under your dash and the alarm tapped into your fuel injection harness
Already seen the above...and have had to remove the alarm in a few cases at work with cars that had bad driveability problems..
Trying to go back to stock without a diagram of the alarm is fun.