What does the owners manual say about it ?

It is about a half hour of covering your bases. Not too bad. Can give you more specifics if you need it. The manual- what a great idea!

What I don't get is why the belt deteriorated. I will have to dig deeper. Any tips would be helpful. Thanks for the replies.

Look at the composite idler pulleys.They may have been damaged or had seized. When you replace the belt, the only things you need to remove are one (either) end of the steering links, a rear loop guide, and the rear actuator rod clip. Loosen the idler pulleys and be sure the belt lays in both the rear guide and the front set which is above a crossmember.Just watch and you will do well.

I will get the belt and idler pulleys today. The rear idler pulley is destroyed and I thought it might be best to replace the other one while I had it apart. It isn't perfect either. It is the machine my church uses and I want to be thorough. It looks like I have to take the steering shaft out- is that right? The bracket that holds the idler pulleys- kind of pivots if that makes sense- will that need to get unbolted to get the pulleys off do you know? I'll ask at the dealer, but I have no manual to go by. I am going to give it some quick maintenance too so I will pick up filters and things. Any suggestions? The guy who normally takes care of oil changes isn't really a mechanic and I just thought this may be a good opportunity to do some. Thanks for your help.

No, the steering stays intact with the exception of removing one end of each of the rod ends. I've learned that when I do Deere's. I remove the easiest one which is normally the front. Belt over the front, up through the chassis in the middle and then over the rear driven pulley. Then make the rest fit watching for the guides I referenced before. The idler pulleys themselves need to be unbolted- not the bracket. I seem to recall one of them you have to maneuver the bolt up so you can get the pulley to clear. Positioning the bracket helps. As far as maintenance goes beyond the placing of parts catch all the grease fittings. The deck spindles, the clutch pivot underside, front axle on each side and maybe one in the center. Blow through the cooling system w/compressed air through the heads, shroud, rear hydro etc. If the engine is really packet, remove the top cover to do a better job. BTW, I think the owners manual is downloadable for free at Deere.com and a service manual may be a good investment seeing as though it is used commercially.