Just bought our first diesel RV two years ago and had the same concerns. It is easy to use the truck lanes. Pull in, fuel up then move forward and park while you go in to complete your transaction. Truckers do this all the time to allow the next user to access the pump while they step inside.
Truckers are always friendly and we have encountered zero problems with any negative attitudes. Sometimes the truck stations have spilled fuel on the ground and even the handles can be fouled. Be sure to check your feet before stepping into a carpeted area............... we keep paper towels handy to clean off shoes.
It becomes easy and is way less stressful that trying to get our 36' gasser into the car fuel lanes when there were no RV lanes accessible.