Just wanted to add my welcome to our forum. I see you are in a period of mourning over the loss of the monogamous dream. You will not get through that right away, so be patient with yourself and with the process.
Keep the communication channels very open between you and your wife. Communicate considerately, but don't bottle anything in. Both of you are in a period of transition right now, so lend each other a bit of extra support.
I hope Polyamory.com will be of significant help to you.
Love means never having to say, "Put down that meat cleaver!"