First, make sure you are staying inside the park gates - the outer gate doesn't open until sunrise, and by then it's too late. You can camp or stay at the Dunes Lodge. Get up early, really early, and make the 70km drive out to the dunes. The last 10km is sand - if you have a good 4X4 just keep it in low, go steady and stay in the middle of all the tracks. If you do all that you'll be rewarded with sunrise amongst the most astounding scenery you'll ever experience. The day we went we had the dunes to ourselves for an hour and a half. Most folks seem to stop at Dune 45 as it's closer ( 45km from park entrance rather than 70). It's nice, but not quite the same.