I have a 99 Accent with multiple problems. First of all the check engine light has been on for a while. I've already been having problems with the transmission slipping into 3rd gear but just recently, my car has stalled every once in a while. So yesterday I brought it to Autozone to check the codes for the check engine light. I got 3 errors back.

PO335 - Crankshaft position sensor: I believe this is causing the car to stall.

PO717 - Transmission Pulse generator A

PO136 - Oxygen sensor

I believe the Crankshaft sensor is pretty simple to replace. The price is about $80.00.
I just want to know if replacing the Transmission pulse generator will fix the slipping into 3rd gear problem? Could there be more problems other than this part?
I don't want to end up spending to much money on this car. I will be getting rid of it in a few months.

Thanks.