I have a Canon Rebel T2i and three lenses:18-55mm, 70-300mm - macro lens, & 28mm 1.8 prime lens).

I've never photographed a wedding before and I've only taken one photography class ever this past summer. The couple asked me to do their engagement photos and now they've asked me to do their wedding photos. I didn't charge them for the engagement photos because I'm still quite new to it all and I wasn't sure if my work was good enough. Honestly I was surprised they wanted me to do their wedding photos. You can see my work here --> www.facebook.com/YPCphotography
I only have my camera body and the three lenses and a reflector. Other than that I don't own any other photography equipment. Is there anything you would recommend me to get and learn to use to help improve my photography?
Do I need to get a new lens for the wedding? And are there any recommendations as to how much I should charge them? What kinds of things goes into determining how much I should charge?

Thanks in advance!!