That's cheap for the box and transfer, while I have never looked under a GT4 it could be similar to an evo where they allow 14 hours to do a clutch on one of the models. Which would still only work out about $1500 @ $100 an hour +GST, so he might be trying to get more out of you but honestly unless someone on here has done one before you won't get much info, it could be an engine out job so 2,3 maybe 4 days labor.