I have an 03 sunfire. Transmission synchro went in 3rd gear and almost gone in 4th. I found a 2009 2.2 eco-tec and transmission out of a cobalt for 600 dollars.
Second that motion. Unless you've got time and money. Long story short, with the sensor upgades the PCM from the 09 will be required to run the engine. The tranny's will swap but have different final gear ratios. The newer tranny is 0.1 taller. If you go this way you will need a programmer to correct your speedo or change tire size. I'm sure you could re-sell the '09 motor.
Looking for a Used Sunfire in your area?
CarGurus has 470 nationwide Sunfire listings starting at $1,700.
Search Pontiac Sunfire Questions
Pontiac Sunfire Experts