Could someone tell me what is the average cost of getting a security sytem installed on a 300SE? I know you can buy the alarm from the retailer and they give you the price installed. But it may be cheaper to buy the alarm off Ebay and then have it installed by an authorized dealer (so I could get the lifetime guarantee). Any opinions? I'm looking at the DEI Viper 790.

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1986 560 SEC *Sold* < Big Mistake I miss my baby!
1988 300SE *Sold*
1989 300CE - current car, but not for too long