Were does she go, for how long, and were can i find her afterwards

Once Serana is convinced to get cured, she will go to Falion who will cure her of vampirism, how long, I am not sure as I haven't done it myself, and neither of the wikis provide information on it either. But I would guess a few days, maybe 3. She will return back to Fort Dawnguard once cured, but like I said, I don't know when.

So ... after she's cured she is like a normal human again? Does her dialog change a lot afterwards? Her abilities change? Will she marry you at that point?

Well, I have found that after the MQ is done, while still being an 'essential' character, Serana becomes.... well... boring. All the side stories, etc disappear, and frankly, she has become just like al the rest. In fact, if you get the bug where she cannot be told to wait or be dismissed without basically ruining your ability to re-up her assistance - she is less entertaining than other followers. With the added ball & chain you face if you happen to like her fighting ability and want to keep it - you're essentially tied to her. YMMV, but I am disappointed with her change.

I, unfortunately, took the route to bring up the topic of being "cured", and was very supportive in her decision. When she returned (proabaly 3 game days later), she said she was back, there was a brief diagloge of actually breathing and being human and THAT WAS IT! She is no longer a follower and responds with that damn "Yes?" Or something else lame.

I'm disappointed to say the least.

What? That must've glitched on you... I had her cured to see the difference, and she does indeed continue to be a follower.

See my post above... She can get glitched. I even went back and loaded my save right after the MQ - left her as a vamp, fast traveled to Whiterun, did some scut work there, saved, then told her to wait...... Did not get the follow option.... So curing is not the issue.

Maybe the fast travel?? I think it is the random luck of the draw on what is/ has been done on your machine... Who knows. I too am bait bummed at this.

Yeah, I wouldn't cure Serana. There isn't much difference, unless you're role playing and there is less chance of having bugs. Besides, I think she looks better with the glowing eyes.

I figured that. Loaded a previous recent save and got the same response. Maybe she's had a few days to adjust and when I get back to Dawnguard, she'll be more receptive. Otherwise, I may have to just marry Lydia on the rebound!