I don't know if this is an easy question or not?

I was planning on going to take my transaxle out of my 1997 saturn sl series because it was recently given to me as a graduation present,I took an auto technology class in high school and we went over transmissions. Pretty much everything about vehicles except the engine. I have to take another year for that class if I want to go over engines, but that's not the point. The point is: I don't have a lot of cash and I know what I would be doing,and a friend of mine said when he tried working on a transaxle he had some gears slip out on him and he had a tough time getting them back in. the third gear will not work on the car and I don't want to spend more than 500 dollars just to get the third gear replaced at a transmission shop. So should I do it myself or take it to a professional? Because I know that manual transmissions are easier to fix than automatics.so what should I do?