I put a Clifford alarm system into my wife's 1989 190e. The Clifford is like any other. I think half the brands are made by the same factory in France, including (I think) Viper.

I hooked up the alarm, the door locks, the parking light flash for the lock/unlock, and the starter immobilizer. None of it was particularly hard, but it took a long time. There is no way that Best Buy can do a decent job with installation included in the price.

The Clifford has adjustable pulse duration for the door locks, so you just set it to the long duration for the Mercedes vacuum locks (no need for fancy relay set up). On the 190e, the vacuum pump is uder the rear seat. I am not sure where it is on the big sedans.

Do it right. Don't use those stupid blue connectors that tap into an existing wire. Solder it and use shrink tubint.

Andrew