I can rough out the 600nm flight to Central Florida in a Cessna 182RG just from memory. Although I would cruise at 155kts, I would flight plan for 150kts. That always seemed to work out as you were at slower airspeed in the climb, but faster in the descent. So a 600nm flight is 4 hours.
My 1978 model carried 88 gals of fuel. I would flight plan for 14 gals/hr even though it only burned 13gph. So, 4x14=56 gals burned. 22gals on board upon landing, or about 1 1/2 fuel reserve in case you decided (or were forced by weather) to go somewhere else.
A couple of notes: I found I preferred 3 hour flight legs, then land and get a soda, fuel, whatever. But flying to Vegas was always 4 hours "on the money" and so I would not add a stop for that. Just pack a few waters and don't drink them early in the flight!!
And, btw, my Cessna 182 had retractable gear. Your insurance provider is going to want to see some actual logged flight time before they are willing for you to step up to retractable gear.
Note: The Van's RV airplanes are great little planes and are very fast and efficient. But, put one side by side to a Cessna 182. In comparison, the Cessna looks like a flying Chevy Suburban, with plenty of room for suitcases, ice chest, etc. Not so much for the Van's RV. It gets its speed from being small and slim. So it speeds along nicely while carrying much less gear.
