Yellowstone is an amazing place. Make sure you take some time to do some research in advance. Two areas that I'd suggest are the history of the Caldera (there are actually 3 of them, if I remember correctly) and the locations of the major attractions. If you are like us, you won't have time to see everything and you'll want to pick the sights that interest you the most. There are some out of the way things like the Virgin Cascades that are really worth knowing about.
We stayed in Fishing Bridge and did day trips to the other areas. You could spend 3 weeks there and not see it all.
2000 Georgie Boy Landau 36' DP
2005 Saturn Vue toad