1999 Pontiac Montana engine, easiest way to change the engi

I bought a 1999 Pontiac Montana and it made a loud noise, sounded like a screeching noise in the motor, we couldn't figure out what the noise was so we bought a new motor for it, my son in law is going to change it and he has done this work before on other vehicles but him or his brother either one is sure on how to get the old one out and new one in, any suggestions on the easiest way to get that done? Please any suggestions will help. Thank You