it'll weigh at least a 1/2T less than the GVW, or about 3000# depending on how it's equipped, but unless you're thinking of a jack that will lift all 4 wheels off the ground at once, the curb weight doesn't mean anything - are you sure you'll never need to fix a flat on the road when it's loaded? do you want to get a jack that's 'just enough'? get a quality bottle jack with a 5 ton capacity and you'll be able to do most anything needed, anything less is false economy
Bill