If it's an early stage it will count as a disease and can be cured as such. If you let it on the last stage like I did, you're gonna have to suck some blood from a sleeping person until you find a cure. When you have some blood the vampire powers will recede a little and you won't get attacked on sight.
In morrowind I was heavily tempted to go full vampire. My most advanced/powerful character was a full caster/mage in house Telvanni and they would still relate to you -- or so I read, so I had a place to go to sell/buy.
Never got around to it. Maybe this time around with a second run though.
I've found a few caves full of them in the northern mountain ranges. I've seen them roaming around outside of their caves near Dawnstar. There is also a good cave full west of Whiterun - Broken Fang Cave.