I doubt very much that you'll be able to find a rebuilt or remanufactured VQ30DE engine for $1500, especially if there is a shipping charge and tax added to the cost of the motor. I think your best bet would be to find a used motor with a warranty. There are a number of used engines on Ebay listed under $1000 with a 90 day warranty. You might also want to check Car-Part.com--Used Auto Parts Market
, which is a salvage yard listing that gives you search options. One thing I would highly recommend you do before you install your engine is to thoroughly clean the mounting flange at the back of the engine where the trans bolts up to, as well as the edge of the trans bellhousing that mates with the back of the engine. Use some sandpaper or Scotch pads. If you don't and there is corrossion on these areas, you can sometimes get a poor grounding issue that will cause radio frequency interferance from the starter while it cranks to penetrate the engine harness and throw off the computer. The result is the ECM loses the referance on the crank position and the engine will turn with a "wrenching" motion like it's timing is too far advanced. It sounds hokey...but it happens!
Another thing is that, depending on the regulations of your state, your not always "stuck" in an "as is" deal when you purchase the vehicle from a dealer, used or new. You should have towed it right back to the dealer. Some states allow for a 24 hour to 72 hour window to protect the consumer from such practices. These regulations are usually listed with the "lemon law" rules for each state.