First of all, hope you have a speedy recovery. Here's my :2cents:, I tend to be a little truck poor at times, earlier this summer I owned 5 at one time.:banging: Had a guy who was hounding me for my 07 cc/sb classic. It was loaded, including sliding roof window, DVD, leather, etc. I had the 06 ec/sb I was building and decided to sell the 07, it had 81,000 miles but had MPI twins, and all the goodies. Told him 36K and he jumped on it. Probably sold it a bit too cheap, now I miss the hell out of it. I had earlier bought an 05 EC dually with less then 40K on the engine and turbo, (GM screwed up when it was in for service and the result they and to replace both) paid 17k for it. Use it to tow the race trailer so it's really not available for personal use all summer. It's a very nice truck, but nothing like my 07. The 06 ec/sb quickly went from what was going to be my daily driver to probably too many mods to make it a comfortable daily driver. So if I want to tow my travel trailer in the summer I'm kind of screwed.
If you have priced trucks lately they are going up in value due to not much out there to buy. I'd check to see if there is much of a market for duallys in your area. I've never known one dealer to purposefully lose money on a deal, relative or not, so I question his motive. Contact the fellow who wants to buy it and see what he is willing to pay if you want to unload it, you might be better off selling it yourself. I got stuck with the 06 ec last year trying to sell it. Bought it to help a guy out and tried to sell it for what I had paid for it and no bites and all I did was pay off his loan. Few tire kickers but that was it, so decided to build it and keep it.
The end of this story is I just bought an GMC 06 cc 1500 with the 6.0 MAX engine with 31,00 on it for 18K. Figured it's enough truck to pull my 26' travel trailer if I need to and I won't be tempted to start modding it like I always do with my dmax's. Sure doesn't have much poop on the top end though.