Transmissions ( Electronic types especially) are not rocket science.
BUT, they can be very intimidating.

That said,,, if your not comfortable digging into the electrical side of it, my best advise is please don't just throw parts at it. Find someone who is familair with the TCM based Chrysler transmissions. Chances are you will ultimatly spend less time, money and frustration in the long run.

There are a multitude of things that can and will cause very similar shift complaints. Thus why you can and will get ( fill in the blank ) fixed my problem type of replies.

Ok, now that thats out of the way and should you decide to dig into it yourself.
My advise is ck wiring . Having been involved in an accident sort of rules out sensor and or internal trans mechanical issues

P0700 is nothing more than a PCM code to turn on the ck engine light alerting the owner there is a code in the TCM

P0731 is just a code to show the gear ratio error occured in 1st gear

P0736 is just the code to show the gear ratio error occured in reverse

As a result of a gear ratio error the trans controller turns off the eatx relay which is what supplies B+ voltage to the trans solenoid pack.

When this happens the trans resorts to limp in mode ( 2nd gear)
2nd is capable because thats where the manual valve is positioned in the valve body thus it allows a non electrical gear application.

Hopefully this all makes sense.