The best option to see the sunrise in dune 45 is having a car, driving to the desert and sleeping in a campground one day before you visit the attraction. If you want to do the easiest and expensive way you also have the option to book a 300 dollars tour that will bring you there. I was traveling with a Japanese guy (Tatsuya), and a French girl (Maud) and we rented a car in Windhoek airport.
It was a holiday and all rental cars were closed, except in the airport. Even though it is a desert with a few unsealed and sandy roads, it is not necessary to have a 4 Wheel Drive, but recommended.
The car was the second cheapest option, an automatic Nissan Altima, available for 95 dollars a day including a complete insurance. We drove 400 kilometres from Windhoek to the campground, set our camping tent to sleep and wake up by 5am the next day. After 4am a few cars already start to form a queue behind the park gate, that opens at 5am. The dunes are exactly 45 kilometres from the camping and after a hard climb, the reward.
From the top of the dune 45 is possible to see the carpark and a great landscape.
Tottally reccomended.