[JerseyGRL1970]

A few days my "wanna be mechanic" friend was "looking for a vacuum leak. I was standing in front of the vehicle with the hood open and did hear something that sounded like a possible leak, but he said he didn't see anything. I took it to Gibraltar Transmissions today. They told me the motor for the 4 wheel drive is bad. I can't locate the part anywhere but the dealership for $383.23.
Could this be the cause of the rough idle and check engine light?
I would hate to go forward with this repair and not fix the problem. At the very least I'll have the shop check for a vacuum leak.