If the clicking is when your coming on of off the gas, its the axel
I had that, and this fixed it .... http://www.350z-uk.com/forum/viewtopic.php?f=9&t=60165&hilit=clicky
Zmanalex can supply complete new units if cost is not a problem
I would however be tempted to go back to the garage that did the work and try to get them to sort it.