yea, changing to a six speed WOULD Mean changing your whole engine...that means you dont know what has gone wrong with the the one youd get, plus the mileage would probably suck...just stick with yours unless you decide to trade in.
umm actually no, you wouldnt have to change the motor. a 6spd tranny mounts up to a motor that had an auto tranny on it the same way. same motors different trannies. you would just have a lot of custom work done to fit the clutch and cutting a hole in the floor for a shifter, and you would have to get a 6spd ecu. theres a long list of things.