Vibrating Upon Accelerating

This is my first post on this site so i hope someone can help me. My brother owns a 1989 Dodge Ram B250 Conversion Van and it use to run fine until we had the valve cover gaskets replaced. We took her to the mechanic and they said they needed to be replaced so we had a trusted friend do so, and that's where the problems started. After they were replaced we took her for a test drive and noticed that she "shakes" when she accelerates from a dead stop or if you rev her while she is in park. I do not believe it is her transmission as it just started after we replaced her gaskets and before that she ran just fine. If it matters, her oil pressure went UP after doing the gaskets and we did not add oil because she has rust on her dipstick so we can't get a clear reading on the level.

Sounds to me like either a spark plug wire was damaged or a spark plug was cracked during the gasket change. Of course if the spark plug wires were removed during the procedure then it is very common to reverse the back 2 on the right when reinstalling them.