Help Please!!

[1996Jeep5.2]

I have some serious problems since the first oil change. OK I'll make a long story Very Very short. Reman Engine, Rebuilt Trans, Rebuilt Rear plus alot of other new parts while doing this. My problem is this after I got the Grand Cherokee back from the shop after many visits all is well till today. My wife comes home "Her Ride the Jeep" she tells me the oil pressure dropped off like it did before the new engine, and it is running rough. So I take it for a spin and sure enough it is. I am know at 3025 mile since the last of the work was performed. I checked my oil and It is about 2 inches past full. What problems could this over filled oil cause? I hope this trip is going to come out of my mechinic's pocket and not mine over $7K deep not including this price of the Jeep. Help Help Help