great advice Rog-thanks.
I went to visit the dealer and picked up a catalog for what accessories fit what tractors in the D100 series.
They have 2 seat covers for my particular model. The cheaper one is 6 bucks more at the dealer and the expensive one is 20 bucks more.
The Home Depot price is delivered to the store, so I can save about 15 to 20 bucks on the seat cover and the mulch discharge blocker over what the dealer would charge.
thanks