Oh you should definitely try to get bub into anterior position. Posterior is generally longer and with a lot more back pain. I ONLY remember back pain with my labour. It was excruciating. As far as labour time goes my 'true' labour was 6 hours. That whole time he was turning. Once he had turned I went from 5cm dilated to 10cm in 10mins!!! Then three pushes and he was out. Oh if only he had been anterior.
I got through just with gas but from what I have heard that is great for a posterior birth and many women need to go for more.
Having said that, maybe yours will be different.