Balljoint is about £15 from VW and a relativly easy job if your handy. I've just today chanded the whole wishbone arm complete with TT bushes and balljoints. Hardest part is the balljoint saying that! Releasing it from the seating!
Could be ARB bushes aswell, they creak more than knock though.
I wouldn't worry about the remap, unlikely to cause anymore damage unless you caine it over potholes etc.
Sam