I thought all '94 325i's were pre-wired for an alarm. If that's true (and I think there should be a little sticker somewhere in your trunk to confirm this), then all you have to do is take out your glovebox area and plug your component into the pre-existing plug/wiring harness. The fob you need for that model "brain" is the 3-button rectangular shaped fob with grey buttons.
<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!