I have a 2004 saturn ion, it sputters when im slowing down,it wouldnt go in reverse but now it does?

I know this is a transmission problem, im just wondering if it could be something with the transmission that is fixable without replacing the entire transmission. The transmission in it is an M75 Hungarian that runs around 3,900 dollars and is rare. And the car wouldnt go in reverse on day then the next it did also was hard to get it going once it was stoped. I had to floor it to get it to move and when it did it would only go about 20 miles an hour.