From one Aussie to another
Hi Sophie,
Firstly, don't worry about the driving on the 'wrong' side of the road. It takes about 15 minutes to get used to. Though I need to warn you, do not drive when tired, very early or very late, as it is at those times that you tend to 'do what comes naturally'. I know I have found myself on the left side of a very lonely road in Alaska. It is at those times you need to be careful. (Shouldn't mention the time I went the wrong way round a round-a-bout in Seattle. lol)
As for a Motor Home, if you do not use them at home for holidays, I would advice against it. Especially if you wish to visit any cities. They would be a nightmare to park. I have even seen folk have problems parking them in parks and recreation areas. As already mentioned, they are no way to save money. A good sedan and hotels / motels / camp ground cabins will be much cheaper, and much more flexible.
As for laying out a route to follow, may I suggest that you get a good map of the US. I find the National Geographics map by far the best. It shows all the major roads and urban centres, as well as National Parks and Monuments, State Parks and Forests, etc. It is widely available in all capital cities, and online. Use post-it notes to lay out a route and mark places of interest, as you make your way through the forums and around RTA. When you have the main attractions and route which interests you, come back here, and the experts here will critique and tweak it for you.
I would have to agree with Dave, and having been to both the south and NYC, I would definitely cut back on the time in NYC and add a little more time to spend in the wonders of the southern National Parks.
Enjoy the planning.
Lifey in Melbourne