Hey Klorinth, from the pictures it looks in pretty good shape. The Kohler Commands had a issue with the valve covers leaking in the eailer years, but I think thats about it. If that motor was taken care of, it has several hundered or thousand hours left in it. The battery may need to be changed soon, looks like a org. battery, or he just went to Simplicity dealer for a new one. I have never had a deck peel paint like that. May want to repaint the deck sometime. Also i see he backed into something, sheetmetal is bent up on the left side (sitting on the seat). The PTO and rear of the tractor look very clean. Need to get a picture of the tiller and snowblower.
If I am not mistakin, the PTO and 3pt were around $500-$600 option new I think. The tillers were around $1500-$2000. Used on E-bay, a tiller will run around $400-$600 if you can find one, like I said they are very rare. I still think $5800 is high. Around here in Illinois, I would say that setup would be around $4000-$4500. It all depends if you find someone who wants a Sunstar with a tiller, they may pay more.
Dennis