Chrysler Repair Questions? Ask a Mechanic for Answers ASAP
Hello, the Po522 code is due to the oil pressure sensor reading low voltage. Since you didnt mention any engine noise the oil presure should be ok and it's just a bad sensor or it's not plugged up.
PO300 is for random misfire. Most often when this happens after an engine swap it's due to a vacuum leak. Either a line is cracked or not connected and could possibly be a bad intake gasket on the used motor.
I would take it back and have them fix the issues since you've got a 30 day warranty.