Dear Karen,
I have been in your place. We got several members of the church that liked to quilt and TOGETHER we helped teach the teenagers how to quilt. With several people we could be all the places we needed to be, at the cutting table, helping with scant 1/4" seams, ironing etc.
I too haven't had the bug to get up in front of folks and speak. But-we finally started a praise and worship service, and they needed people who could sing--and I felt the Lord tugging at my heart. I asked a friend how she could stand in front of a microphone and sing, and she told me she prays, and does it for God's glory, not her own. When put in that form, it is different. Remember, God doesn't call the equiped, he equips the called.
One other thing, I would guess you know some of the people that will be in the class. Can you think of them as your friends? That your friends are there in a get together, and you are showing them something they want to know about? It seems easier to talk in front of people you know and care about. If all fails the old tip of imagining them in their undewear might help de-stress you!