Yes, that is the Ford weight decal. There should be a GTRV decal as well with possibly the CCC, cargo carrying capacity.
The GVWR is 7000 pounds. I'd want to know what the weight is now with the conversion. The GVWR minus the weight is what you have left for people, fuel, water, supplies, etc. 7000 isn't too bad, but weight adds up quickly.
The van needs some work, so I'm with Grampswrx on offers and negotiation. Finding one that will fit in the garage at 6'9" will be a challenge. Factor in what it will take to fix. You might want to get a quote to take care of the under carriage.
2008 GMC 3500 Quigley Weldtec 4x4 Savana SMB