I looked up what drives you have and they are relatively easy to work on. Depending on weather you are changing one or both makes it a little different.
1. Jack up mower so both rear wheels are off ground.
2. Remove wheel/wheels for pulley replacement.
3. Remove drive belt from pulleys.
4. Remove parking brake. I remove the screw that connects it to the trans.
5. Remove drive linkage.
6. Remove 6 mounting bolts. Trans will come out.
7. Remove nut holding fan and pulley on.
8. Remove fan and pulley.
Reverse instructions for reassemble.