E30: turn signal turns on brights

I've searched the net and haven't found a solution to this problem yet.
I own an 87 325iC. Starting about two years ago, with my headlights on,
whenever I used the turn signal and completed a turn and it would snap
back to the normal position, my high beams would come on. I explained
the problem to a mechanic that told me it would cost about $800 to fix.
I decided to just not use the signal lights at night. Now it's gotten
worse. Whenever I turn on my headlight, my high beams come on and I
can't turn them off. If I jam a peice of folded paper behind the turn
signal stick, it will move it up enough for the high beams to turn off
but then I can't use the turn signal or the paper will fall out and I'm
back to brights.
Has anybody else ever experienced this? Any idea what could be causing
the problem? How hard would it be to fix this myself? Thanks.