I love my 6.0L 2500 Burb. But I have a newer one, a tiny bit more power, and far better gearing of the 6-spd. The older 4-dps with 6.0L I personally do no recommend. The 8.1L with either axle ratio are just that much better for towing. Everyone that has the 6.0L says towing is acceptable performance. Everyone with the 8.1L says towing is a dream.
Towing fuel use is the same. Non towing the 8.1L does suffer quite a bit from the 6.0L. I would say 20% more non towing fuel cost for 8.1L. So if you expect a lot of non towing miles, the trade off may be worth it for you. Plus there are far more 6.0L available.
Movies on the road? Uou can buy a single portable DVD player for about $60 and dual screen systems with velcro straps to the headrest for under $100. The integrated is nice as parents can control easier. And today's mobile devices like iPods/iPads offer a lot of versatility to entertain the kids while traveling. Anyway, they are nice. We had OEM DVD in our last 3 family vehicles and still use it. But there are other solutions so I would not prioritize it in the already low inventory of your target vehicle.
I cannot comment on independent vehicle assessor. Maybe find a local mechanic in the same area as the vehicle?