If you are unsure about the stud size, take one off. It is stamped in the lug. Should be 9/16". When I had to replace mine do to what my dealer did, I found it stamped on the lug nut. I have not used a dealer for service since. Should check torque after loosening lugs after 200 miles. Then at the end of the day of driving. I check the torque before I take the next trip after that. I never have had them loosen, but I have read on the form that other owners have. My dealer over torqued and ruined the lugs and lug nuts. I had to replace all.
Have a Big Horn with 6K axles. The Landmark, Big Horn, and Big Country are build on the same line.