For some reason I thought this chassis was a Ford, and answered accordingly. Sorry!
Your tires won't be anywhere near max on a Sprinter-based Class C, so I'd say shop for LTX M/S2 or TransForce.
I'd expect Sprinter to handle better than Ford. The Chevy fans'd be saying "What Doesn't?" but if your Sprinter felt vague on your trip home AND you had adequate tire pressure, I'd still say Sway Bar.
I'm sure somebody can chime in about Koni FSD shock availability for Sprinter. Those are the ones you really want if you want to Cadify (Benzify) your ride. With only 15000 miles I'd say wait on shocks/struts if they are NOT available now in FSD. See if they show up soon.
