Can anyone give me info on Denali National Park in Alaska?

We're driving to Anchorage this summer and hope to have time to stop at Denali. Unfortunately we're driving more for business than pleasure so won't have a lot of time. Is one overnight enough, and do you know how hard it is to get a campsite there? I'm not sure - I know at Yosemite it's first thing in the morning to get one.