re: Any suggestions for someone doing a Prime Rib for first time

All of the above methods will be great if you don’t overcook. You need a reliable leave in thermometer and also a reliable instant read thermometer. That might be an investment, but you don’t want to ruin a costly hunk of meat, and if it gets over 135, you won’t be satisfied, I know from painful personal experience. You can always cook it more, but you can’t un-cook it.