Jim, it's been a while since I last replaced mine but it not that easy. As best as I remember, you first got to lower your hydraulic oil level in other to r/i the front hydraulic pump which will allow you to removed the hyd. pump shaft your were refering to in your post. Now it gets a little tricky. In order to unscrew that shaft out because it is indeed screwed inside the drive plate you can see bolted onto the front crankshaft. Don't forget, THE SHAFT IS IS LEFT THREADED, meaning you have to go clockwise to unscrew it, just as if you would tighten it. The best way to unscrew it is by using an old spare hydraulic pump shaft with a nut welded to the none-splined end and use an impact wrech to uncrew it. It works wonder. Otherwise, it could get you mad. If not stuck in there, you succeed working the shaft loose with a pair of vise grip on the section between the adaptor plate and axle housing. It's not a good way of doing it though.
The first time I replaced the water pump/alternator belt on mine, I borrowed my MF Dealer Hydr. shaft to uncrew the get my drive pump shaft out. Once that's done, you still won't have enough room to pull the belt out, at least not on mine.
You either have to remove the four screws holding the pump drive adaptor plate that is bolted to the front crank. While you're at it, you may want to replace the rubber bushings in there it if they they show signs of wear.
With that plate removed, I think but I am not sure, you may still not have enough room to pull the belt out. If so, you will need to loose some of the front bolts (4 of them I believe) that holds the front axle to the front of the engine just enough to allow the belt to come out. Try prying it apart once the bolts are bakcked off if the front axle doesn't want to move forward.
I piece of advice, install a good quality belt. You don't want to have to replace it again in a while.