Trunk won't open, how can we fix?

[mudman]

My buddy has an '88(?) 325e and his trunk won't open. It was semi operable until a tire tech used a screw driver on the lock to open it (he had snow tires put on and the tech was putting old wheels/tires in there).

Yesterday my friend was trying everything to get the trunk to work when he broke the key off inside the cylinder. Now what? What is the best way to gain access to fix the lock button assembly?

Thanks!