I would just let him see what he finds--I still say with 2 dead cylinders hitting 65 would be a pain and it would probably buck and stutter --really the oil sending unit is one of them thing where you can get a bad one pretty easy, I replaced 3 in my wife's intrepid in less than a year.
Get a second opinion and hopefully it will just be something easy ,
I will tell you that at 90,000 miles you will be looking at the timing belt and water pump and maybe the belt tensioner which will suck to the tune of close to $1200 or so btu that is the life of a PT owner
