Help! 1996 E320 Window Busted!
 

I was in my 1996 E320 today and the driver front window wouldnt work. When I went to open the window i heard a loud pop and the window slid down. I can (by hand) pull the window up and push it down. I took the door panel off to find nothing visually broken. No chards of metal, no pieces of anything, not even a screw in the traugh. I noticed a metal arm that was hanging and i guess it would be connected to the motor. Is this the window regulator that broke? Is it an expensive part? I am a major DIYer` so i think i can tackle it, but since nothing is snapped or scraped I don't know what is wrong!?

Mike-
Any thoughts and all suggestions would be appreciated.