Your owners manual should have a max combined weight that includes the truck and trailer. Most newer 1/2 tons with a max tow package would be capable of 7000 lbs but since your truck has the lighter duty package it may be only good for 3500 to 5000 lbs. Find out what the differences are between the two packages. The max package may have better axles, springs, electrical, and increased cooling for the trans and engine. Personally with older trucks I would limit the 1/2 tons to 5000 lbs and go for 3/4 tons for anything bigger. I also installed the biggest cooler I could for the transmission with an aux fan.
Yes you should use a WD hitch.
"Nelly Belle" 95 XLT SC SB 300 4x2 5 spd 244k
"If women don't find you handsome at least let them find you handy" Red Green