The answer to your pricing question is - 'It depends'.
Do you want to sell it quickly to the first person to look at it? Can you wait a month or two while the looky-loos show up in their minivans with no cash in hand?
If I were selling it, I would ask 5500 and get it sold by the end of the week for 5200 or 5 grand, give or take. Some may ask 6500 or 7 grand and have to wait and wait. Depends upon your needs and your situation. 778 hours is low-ish for a tractor but not low for a SCUT.
Sorry for the family's loss, and I hope the sale is quick and hassle free.