Help me plan a trip to Black Hills/Mount Rushmore?

I am going to Mount Rushmore in july from the 4th to the 7th and I don't know what I'm doing and I am running out of time. Its over the 4th so of course a lot of the hotels are booked. This is my boyfriend and I, and id just like info on where its cheaper to stay like Rapid city, Keystone, Deadwood etc. and id also like some info on things to do. We've got about 1000 to spend, prolly about 100 of that going into gas. Best answer goes to the best info and the best planned out vacation. Thankyou :]