should take someone whos done the job before about 8 hrs to 10hrs for a gtr lowmount turbo swap. so about 400 to 600 bucks..
if they havent done it before dont bother getting them to do it as you will pay for many more hours labour..
also some guys drop the engine and gearbox out and then its very fast to do the turbo swap.. but price would be close as the above way,,,
cheers.