Rear derailleur hits spokes when switching to largest sprocket I accidentally ran a bungee strap through my old rear deraileur and it tore it apart. I have fitted an identical replacement but cannot work out how to adjust it so that the tension pulley does not collide with the spokes of the rear wheel. 

The original rear derailleur, damaged



(hi-res version here )

Originally I bought the bike new from the LBS, who built it. It looks like they may have bent deliberately the metal frame that holds the guide pully but I'm a little anxious about trashing a brand new derailleur without confirmation that this is the best solution.

I ride a Surly Crosscheck and this rear derailleur is the standard spec so it seems more likely that the crunch has damaged another part or I have misfitted the rear derailleur.

What is the likely problem that is causing the guide pulley to collide with the spokes when I switch to the large sprocket?
I guess the derailleur hanger or the bit of frame it connects to must be bent. These can be bent back. Of course Sheldon Brown has some advice, but I'd be afraid to do this myself and instead take it to the LBS who will have the tools.