I know this is not RR/AX related, but this seems to be a great thread for truely experienced...

The nut that is locked in the chassis that the bolt for the compensator arm to bolt to the chassis is no longer there. I stuck a magnetic extension in there and I've got nothing.

How screwed am I, how do I go about repairing this.

 

Get a circular saw and go in from the inside of the car. Not that hard really.

 

I shouldn't be too concerned with structural issues?

 

To prevent any cracking of the tin, you can weld a ring around the opening you just made.