If the chain has been twisted about enough it could have twisted the front mech cage out of alignment too. The rear mech on my wife's road bike recently dived in to the spokes, to sort it out fully I ended up replacing the rear mech (£15) front mech (£15), chain (£11).
Maybe it's a daft question, but do you need to replace all the cable when replacing the derailleur like for like, or can you use the cable that is still there?
I've already spent £20 on the rear hanger and a chain link, each derailleur is approx £30 I think (105 10 speed) and I would ask the LBS to do these as it begins to cost so much it's worth getting it done properly, and I reckon having to change cables means even more work, and bar tape etc? Don't get me wrong, it needs doing, just wondering on likely overall cost.
I am just hoping now the wobble in the back wheel is just out of true, and not a bent rim.