Thanks for all the replies everyone.

The car is currently sitting in my employers parking lot, awaiting a tensioner change or a tow home for wrenching.

Quick question: S-Class, you said that the threading would slip out the other side - does this mean that I could potentially repair this tensioner and just get the torque bolt installed and be on the road again?

I know I should probably do the whole shebang, but I'm trying to avoid towing it home and in its present location I'm not certain how effectively I can work on it. At least it's under covered parking though, and it's been rainy as all heaven here in San Antonio as of late!