Welcome to our forum.
I think your new friend is giving you good advice, and taking it slow, while tending to your SO, is the key. It probably wouldn't hurt to talk with the wife, just to get on the same page with her and offer your support.
Sometimes people plan ahead of time to be polyamorous and make a well-controlled entrance into poly life, but it is probably more common for someone to "fall into a poly situation" and learn what poly is afterwards. I certainly had some general changes in personal philosophy prior to my becoming poly, but I rather "fell into a poly situation."
You will certainly have opportunity on this site to talk to people that understand your situation, and get a better understanding about it. Have a look around at our various threads; there's a lot to learn here.
Glad to have you aboard.
Love means never having to say, "Put down that meat cleaver!"