Depends on what kind/year car you have. You may be able to do it yourself. For example, my 94 325i alarm is part of the keyless entry system and is not in the key, but on the key fob/chain. Also, this was an option on these cars, and therefore may not be on your car. If you have this kind of system, you need to take the chip out of the key, place it into the alarm main box (behind the glove box) and hit a button to program it. If you have an alarm system, but no key fob thing, you can buy it on ebay for a fraction of what the dealer is asking. If it's not an E36...then this was just an interesting story for you to read!
<span style='color:green'>1994 325i </span>- - - 75,000 mi.
No mods - - - very happy as is!
<span style='color:green'>1995 525i </span>- - - 154,000 mi.
No squeaks or rattles... unreal!