I went to visit a Himba village about 20km from Opuwa... no idea of the name of it though, sorry. Easy to get to in a 2wd though. The guide (who was 'ex-Himba') came in my car and directed. Just ask the people wherever you end up staying in Opuwa. Seems like a small tourism network is building up there, and you'll probably end up being sent with a guy named Jackie (or Jeckie, I think). I was passed though about 4 hands... and ended up joining up with a small group of 4 others. Was very interesting. We took gifts of cooking oil and maize flour. He'll help arrange all that and tell you how much is appropriate etc
Not really much else in Opuwa (that I saw), so 1 night should probably be enough.