In excellent shape you should expect around 7g for it. People do not pay for modifications and usually don't pay top kelly blue book pricing either.
I would of taken and ran with the 7k cash offer. Unfortunately you owe too much on it so you wont sell it with out taking a loss.
Sucks but you still have a nice ass truck and maybe with the right price someone would buy it. I'd recommend removing the suspension lift and selling it. and then selling the vehicle for a lower price. Perhaps that way you'd make a little more money.
I welded the track bar bracket to the frame gona be hard to remove it. Suggested retail is 9,3xx. I still owe 8300 so I wont go any lower than that. I want atleast payoff. I now people dont pay extra for susp mods. A truck looks better lifted then at stock heaight. I did all the lift myself and it been almost a year its been put in. I can take 2" susp out by taking the spacers out. It will 8" instade of 10". Thanks for the comment The truck hasnt seen any mud eaither.