Getting to Mrauk U is already quite an adventure, you should count 2 days travel each way. You can go by bus all the way but we decided on the more comfortable alternative, flying from Yangon to Sittwe, then by private boat to Mrauk U.
We had to overnight in Sittwe (hotel Shwe Thazin, clean but very basic), the next morning we got up early and took our pre-booked private boat up the Kaladan river, which took us about 7 hours. We very much enjoyed the trip in our open boat, much better than in a hot cramped bus!
In Mrauk U we stayed in the Vesali Resort (a big name for a nice but also very basic place). The staff though was lovely, so helpful. Don’t expect them to speak English though.
We spent three days here, visiting the village and the temples and on a day trip up the Laymyo River to see the villages of the Chin tribes where the women with the tattooed faces live.