I just finished rebuilding two hydros over the past couple months--my 149 just last week.
The service manual has very good instructions on how to disassemble and reassemble the hydro unit. Follow them carefully and you will not have problems.
While J-Mech is correct, some parts have very fine tolerances, it's not too difficult a job if you are careful and take your time, and work in a very clean area. I put my hydro in the parts washer and get it squeaky clean before starting the process and work on a clean bench with an area to set parts down in the order they are removed.
Basically, you remove the charge pump, then the case front, and finally the pump and motor cylinder and piston sets. That exposes the swash plate. Using a punch with a depth mark at 15/32nds, you tap the pin into the shaft (see the service manual) and the shafts will come out. Replace the seals, remove the pins from the shafts, and re-install the shafts with the pins. Again, it's critical to read and follow the service manual instructions exactly.
There is some side-to-side play in the swash plate shafts--probably .025 inch, and that is OK. for the third question, I think you want the trunnion springs to take up any play between the cam and trunnion plates.
In both cases (my 1450 and my 149) the rebuilds, including new trunnion "rectangles" for the springs welded on, and new springs, I found that the tractor performs MUCH better, and the hydro maintains speed much better. It's worth the effort IMO. I plan to rebuild a couple more to solve speed drift issues.
__________________
|