Remove the PTO idler spring. A piece of starter rope works fine for this task.
Roll the belt off the front spindle pulley.
Take two flat blade screwdrivers and lift the tab on the clutch pigtail with one while using the other screwdriver to separate the plug halves.
Take two ½" wrenches and remove the two bolts / locknuts that attach the clutch to the clutch stop. Pull the clutch stop off its post after removing the two bolts. (It's fine to let it hang by the tie strap attaching it to the clutch pigtail.)
Take the PTO belt off the clutch. Put a 3/8" ratchet extension into the pump idler arm to release the belt tension and drop the belt from the pump.
For installing the pump belt, it's easier to route the belt around all the pulleys but NOT the right-hand pump. Next attach the spring keeping a little tension on the belt by pulling it toward the right-hand pump pulley. Now use the 3/8" extension again to move the idler enough to roll the belt on the right-hand pump pulley. You can also route all the belts first and then try to put the spring on, but that's a bit harder.
Put the PTO belt back on the clutch pulley, reattach the clutch stop and plug in the clutch pigtail.
Attach the PTO belt spring before you put the belt back on the front spindle pulley. Note the routing of the belt.
Put the belt back into the groove of the center spindle pulley and roll it counter clockwise to finish installing it.