Wow, I got to learn something new today; I didn't think the Hemi was available in a Ram 3500 back in 2006! I thought the Cummins was standard on 1-tons until very recently.
My thoughts: it sounds like a really cool truck (love the rare manual trans/gas engine combo) but I think they need to work on that price quite a bit. (I assume it's at a dealer?)
Over 140k miles and a gooseneck hitch mean that thing has done it's share of work and if I was considering it for purchase myself I'd like to see the price reflect that.
To me, even if in really nice shape, it sounds like a $11500-$12000 truck but that's just my opinion.