So, i was playing Morrowind and wanted to got to Molag Mar, starting from Suran.
I followed the road and the signposts, like a good boy, and after two or so days of (in-game) travel i suddenly got attacked by some skeleton guarding a certain tomb (Vorani tomb or something)

I killed the skeleton and went into the tomb, only to get attacked almost immediately by a halfnaked man with completely white eyes. I battled the "man" for a long time, wasting a lot of restore health and fatigue potions and when i finally killed him, i was halfdead myself. The "man" literally squeeled like a pig when he died, which was very strange, since i never heard anyone die like that before.
I didn't go further into the tomb, because i had enough trouble killing this unarmored guy, let alone the possible dozens of others like him in the tomb.

Anyway, i checked the halfnaked dead man for loot, and got a message saying i entracted some sort of disease, pohyric hermophylia or something like that. I decided to heal myself as soon as i got to Molag Mar. But later on, when passing the silt strider near Molag Mar, i noticed that the only effect thing i got from this strange disease was "restore fatige +1"

"Sweet", i thought, this disease only has a positive effect! And i sure can use some extra fatigue on my travels! Anyway, i decided not to heal myself, although everyone told me to do otherwise. After repairing my weapons and a good night's sleep, i headed north, to visit the Telvanni side of Morrowind.

A couple of days later, i woke up at 4am in my tent (Adventurers tent mod) and got a message that i got a strange dream, involving a lot of blood and a blonde maiden. I noticed that i gained A LOT of new ablilities, and saw that i have "Vampirism."

My eyes where white and i looked really vampire like, then i panicked, since Vampirism gives you sun damage and it was already 5am. Fortunately, i could reall to my house in Suran before 6am, and since then, i've been feeding on rats, kagouti, guars, and even cliffracers. I haven't revisited the tomb where i got porhyric hermophilia yet. I don't know wether the vampires will accept me as one of their own or attack me because i killed one of their "brothers".

What should i do? I like the fact that i can sneak right in front of someone without him/her noticing it, i like the extra speed, acrobatics and strength, but i hate the fact that i haven't seen the sun for a week now (in-game time), which seems like a very long time! Later on, when visiting Vivec i read in Vampirism in Vvardenfell that Vampirism is incurable and irreversible. Is that true?
And can i finish the MQ as a Vampire? I'm afraid Caius won't talk to me, or even attack me like those stupid Ordinators...

As long as your disposition with him was high enough beforehand you should be fine, you'll have some problems with dunmer characters such as Mehra Milo though, stock up on charm scrolls/spells and Telvanni bug musk.

Vampirism in not incurable though, it can be reversed if you want. There is a quest to do so. (I'm not saying where or how to find it though, you'd beter ask in the spoilers forum if that is what you want.)

Thank you, i just read Vampires of Vvardenfell Volume II in Tel Vos, and am now heading for Sadrith Mora to see if i can get more info on the cure (At least Telvanni talk to me)

I'll try and find the cure.