Dear David,  

1) If you were validly baptized as protestant, that is, through the pouring on of water with the invocation of the Blessed Trinity and the intention to incorporate you into the Mystical Body of Christ, then there is no need for you to be baptized. If you are in doubt about this, you should check it with the congregation you belong to, and then consult with a priest. If you find that you were validly baptized, then you need only be fully received into the Church. In that case you will receive the sacraments of Confirmation and the Blessed Sacrament. You should also make a general confession as a preparation to your full entry into the Church. 

2) When can you be baptized? 

Any time! If you request baptism from a priest, then he should administer it to you. He may judge it necessary for you to wait until you are sufficiently ready before administering the sacrament. Otherwise, he may proceed to administer it almost immediately. Easter is generally chosen for the baptism of adults or the reception into full communion of Christians because it is particularly apt to communicate the reality of the Mystery that is taking place. It is also following the ancient practice of the Church. 

3)What about RCIA? 

This you should see with the parish priest. He will be able to guide you on this point.  

God bless you and take care!