Why is my 2002 dodge ram 1500 not wanting to pull in drive and not wanting to switch in second gear?

I'm having the same issue. No drive, reverse or anything. I know my o2 sensor is shot but it's throwing codes on o2 sensor, pressure sensor, gear ratio and many more. Let's just say it lights up the scanner like a Christmas tree. Engine replaced 2 months ago (57, 000 mile engine) and tranny also at the same time. I don't drive like an animal, yet I'm thinking I should of. The truck when I bought it was in amazing condition on the body, knew it was ran hot and what I was going to invest into making it drivable again. Seems to have MAYBE had a tree fall a top it due to the fact the roof is black and the back Window looks like it was bubble gummed on and a dent on then tail gate. I love my truck, hate the 4.7 engine. The mechanic seems to think it's the crank shaft that went out so gonna change that and fix the sensor issue and pray that nothing else goes wrong. Did you find out why yours had this issue? If so, please let me know if something else other then what the mechanic says it's wrong with mine.