Hi Ian
Compression arm failure is common on the 350Z, if its the bush thats gone then these can be replaced if its the ball joint then the complete arm is required.
We can supply both and for the bushes either OEM Nissan ones which are not available from a UK dealer or aftermarket from Whiteline or Supepro.
Its a straight forward job but I wouldn't trust Kwik Fit to change a tyre let alone a suspension arm you would be better finding a real mechanic, where about's are you based i'm sure someone can recommend a good garage?
Ewen