You should also make sure it is just the turbo before you start handing out money.
Drain the oil and look for metal shavings. Depending on how your turbo went, you may have introduced metal into the oil system which can take out your shortblock quickly.
Highly recommended to do an oil flush, clean (or remove) the banjo filters around the turbo and if there are shavings you need to replace the oil cooler.
Good luck! And like everyone else said... run away from the dealer.