Since you don't have a Parking Brake on a 5er, the wheel chocks take on that function, so yet you need some, nothing worse than pulling the hitch release and seeing you Rig start moving backwards toward that beautiful lake (LOL). King Pin stabilizers are more of a personal preference. We don't use one and don't want to carry one with us, we feel the Level-Up System does a great job and about the only thing better would be cement blocks. So give it a try without one, then see if a friend can loan you one to try and you make the call.
Michelle & Ann
2018 Chevy 3500HD Crew Cab High Country DRW, D/A, 2016 RW39MB, Dual ACs, Auto Level, Auto Sat Dish, Stack W/D, King Sleep #, 17.5" Sailuns w/Disc, MORryde IS & Pin, Comfort Ride Hitch, 5.5 Onan, Res Fridge & Induction Cook Top