Analyse this position ( early game )

Note that I could of also played (for black) 3. ...Nf6
What I wanted analysed was the BxN move. Black now has doubled pawns. I have been told that this does not give any player an advantage, nor a disadvantage.
My questions:
1.Is black now almost Obliged to castle queenside, in order to use the doubled pawns?
2. Can black easily undouble his pawns?
3. Can someone post a game(s) where black gets doubled-pawns ( because of BxN) and where he manages to undouble them, or make better use of the situation?
I want an example to see how black doesn't lose equality because of the D-P (doubled-pawns)
Well I'm not an expert player or anything but just from my own experience:
1. No, in fact black might prefer to castle king side because pawns that haven't moved yet are generally harder to attack. What do you mean by "use" the doubled pawns?
2. No, it depends on if white chooses to exchange or if black can force it.
3. I don't have any games offhand, but just look up the Ruy Lopez opening. I think this is the exchange variation... studies on it should show you how to equalize. Basically though black is not at some huge disadvantage just because he has a pair of doubled pawns. If you do count it as disadvantage, then you can say you have compensation because he traded bishop for knight and bishop is slightly stronger.
By the way if he takes your pawn with knight, play Qd4, attacking his knight and e pawn and he can't defend both.

Yup, it's just the Ruy Lopez exchange variation. If you wanna learn about it type it into google
-black has the bishop pair after the piece trade, white does not. White gets rid of his Lopez bishop which is often a powerful weapon useful for such things as sacrifices on f7 and other kingside attacks
- black doesn't have to castle kingside
- black isn't particularly motivated to undouble the pawns. It's not that important

All of the above good answers are SOP (Standard Operating Procedure). Also, your idea of exploiting the doubled queenside pawn structure is not new. There are lots of games from GMs in the late 1890s to early 1910s that illustrate some of the plans tried by White. Some especially instructive games with this idea were played by Emmanuel Lasker.
And, I would add that you should also google The Scotch. There are a whole set of variations in the Scotch opening where Black's queenside pawns are doubled exactly as they are in the Exhange variation of the Ruy Lopez.
But, more to the point in those Scotch variations Black sometimes castles 0-0-0. Those lines should give you some ideas about how White can sometimes exploit Black's Queenside castled pawn structure.
I hope this helps.
to amplify on omnipaul's comment: the doubled pawns aren't a major immediate disadvantage--but if white can manage to exchange down to a K + P ending without altering the pawn structure, he has a straightforward win; white can create a passer with his healthy kingside majority, while black can't with his crippled queenside majority. luckily for black, he has some important middle-game edges as noted above--the bishop pair & freer development in an open position. white often plays for an early ending by forcing a queen trade via d4, exd4, Qxd4, Qxd4.
What I wanted analysed was the BxN move. Black now has doubled pawns. I have been told that this does not give any player an advantage, nor a disadvantage.
My questions:
1.Is black now almost Obliged to castle queenside, in order to use the doubled pawns?
2. Can black easily undouble his pawns?
3. Can someone post a game(s) where black gets doubled-pawns ( because of BxN) and where he manages to undouble them, or make better use of the situation?
I want an example to see how black doesn't lose equality because of the D-P (doubled-pawns)