Do I need a new transmission for my 2004 Chrysler Concorde?

I have a 2004 Chrysler Concorde with 155,000 miles. The engine light had been on for quite some time after i got it out of the shop for power steering problems. I was driving one day on the highway and it randomly started to slow down although the speedometer read that I was going 65. Then as i was trying to pull over, it started smoking and the oil light came on and the car stopped. I took it to a mechanic who said I need a new engine. Then after i got that taken care of, he tells me I need a new transmission, sensors and oil pump because it's not switching gears. Does this sound legit? Should I even bother getting this fixed or should I consider getting a new car?