Classical guitar pricing can be quite tricky and subjective. In the end it's really a matter of what one is willing to sell it for and how fast they want to sell it. Seeing it is from your dad, I'd simply ask him what he is willing to let it go for. He might give you a great deal!
Subjectively I'd personally price it around $4k based on my knowledge of Kenny Hills guitars. If I really liked the guitar and wanted to buy it myself, that is as high as I'd go, but would preferably want it lower. If I were buying blind online without being able to try in person, I wouldn't go beyond $3k.
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