BlueAngel, welcome to the world of polyamory and to the forum.
I can offer you some reading by a very good writer called Franklin.
Polyamory for the Monogamous: http://www.xeromag.com/fvmonopoly_existing.html
Things to Consider Before You Enter a Relationship as a Secondary: http://www.xeromag.com/fvsecondary.html
Guide to Dating a Couple: http://www.xeromag.com/fvpolydatingcouple.html
Those have some excellent advice, I feel, for people in your sort of situation.
I hope things go well for you!