Don't be over ambitious. Our first RV experience was also a rental. 15 nights, 2500 miles & we were busted at the end.
First day is picking it up, stocking it & not getting very far after that. Last day is returning it. That leaves 6 days. Not much time but you might be able to pull off a Zion, Bryce Canyon, Grand Canyon & Hoover Dam loop. Zion, Bryce & Grand Canyon will need a full day each to get the quick whip around tour. Then there is the commute between each with time to stop to ooooh & aaaaah at various viewpoints along the way.
