Before you go buying an alarm system...check behind your glove box (have to take it out, there's a thread on this) to see if you still have the main "brain" for your alarm system. If so, you'll only need to buy a key fob/remote for the alarm. I think for your model year, you can pick one up from e-bay for around $30.
<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!