Could not disagree more strongly- and Downey is not up on the 3.4, only old school swaps.

Check the exhaust crossover work, it can be a real nightmare. A motor swap can be simple and clean, or it can be a real hack job, it all depends, but is usually fairly obvious on close examination.

If it is a 3.0 to 3.4, most of it will probably be decent. +1 on pulling the codes, and beware if the guy has reset anything. Emissions laws may require a state inspection and certification, mine did; wasn't a huge deal in Colorado though especially since Mike Caskey did such an obviously clean job.