2000 Chevy Cavalier

Hello,

The car is actually a 2000 Chevy Prizm but that didn't show up as one of the options!

My engine started burning oil and for months I just put in oil every week. Then recently I drove it too far and it finally was ruined. So I paid $2000 to put in a used engine from the exact same year and model. When I picked the car up, it ran okay for a day but suddenly it wouldn't accelerate and came to a complete stop. After about a 1/2 hour of sitting I tried it again and it worked, but only temporarily. So I brought it back to the shop and after FOUR DAYS they finally gave it back to me but with no real diagnosis. They checked all the connections between the engine and the transmission and nothing seemed wrong. Then they took the transmission out and looked at it (I'm not sure exactly what they did) but they put it back in and said it seemed to be working fine again so I could come pick it up. Well, it got me home, but I'm not at ease yet. I have noticed two things that are different about it:

This might not mean anything, but even though the vent is turned to "off" it still blows air depending on how fast I'm going- the faster I'm going the stronger the air. I noticed this the first time I picked it up so I don't know if that has anything to do with it.

The major thing I notice is that when I shift from park to drive, it gives a big jolt- never used to do that. The makes me afraid there's still something wrong with the transmission.

I never had transmission issues before I got the engine replaced.

Any clue what is going on?

Thanks!
Hannah