Some like to use the truck stops because of the ease of entry and exit but I try to avoid because of the much higher cost. If possible I will fuel at a store away from the truck stops and only use them as a last resort. Gas buddy, google earth and reviews can give a pretty good picture whether you can get in or not.
To answer one question, yes just line up with the truck, and other big rig diesel users, and get fuel. Some truck stops have credit card machine at the pump but not most. Some Flying J have RV lanes but not all. Access to Flying J RV lanes can also be tight and may require careful maneuvering. Here in the south a lot of regular stations have a couple of separate diesel lanes set away from the regular gas lanes offering easy in and out. Marathon often does that.