Chaplainbill, I do pizza on my gas grill, no stone. I buy a ball of dough from our favorite local pizza place, and use it as is (about 1 lb.; makes two ~ 12 in. pizzas). Roll out to your desired thickness, coat well with olive oil and proceed. I use direct high heat (around 500 F.) on the first side until lightly browned (2 - 3 minutes), flip to the other side off the grill with a large spatula (and fingers) onto a rimless sheet pan (corn meal on the pan helps to keep it from sticking), add toppings and cheese, and slide back onto the grill using indirect medium-high heat (so the crust doesn't burn right away and the cheese has time to melt). Close the cover and let the cheese melt (3 - 5 minutes). I always use thin-sliced or shredded cheese at room temp.
I'm sure these steps can be adapted to your PG 500. It makes a rustic pizza with a slightly charred crust, which we like on the thin side. Good luck!