Hello revilo -- welcome to the Forums!
The Sport is a line by itself. It was intended to be more family friendly (less cost) and a touch lighter. It's available only in 17' or 22' lengths.
The Safari became the Flying Cloud a year or so back. The new Flying Cloud is generally equivalent to the Special Edition Safaris of approx 2005-2007.
Even in the half ton, the Express should be able to handle 4500 gross trailer weight. See 2008 Chevrolet Express specs, auto safety at Edmunds
. It's got a generous payload, so could handle the tongue weight and maybe 4 adults with some other gear inside. Just don't fill it to the ceiling. Googling, I see some mention of 3.42 or 3.73 rear end ratios. The lower axle ratio isn't great for towing. Driving with a 3.42 might be a dog on grades and you'd have to slow down. Your dealer might be able to read codes to tell you that number (inside glove compartment door?).
I'd say what you have could be made to work. Issues to address would be whether it has a Class III/IV hitch
(should be something available) and checking out wiring harness issues for 7-pin umbilical. Your dealer could tell you if there's a plugin for a brake controller pigtail somewhere under the dash. And check out extra transmission cooler add-ons.