Welcome and enjoy the group!
GO SLOW! TAKE YOUR TIME! If you do go all the way, put a curb on your hormones and desires to put it all the way in. Let her be the guide and determine how much to take. As far as positions, try her on top which allows her more control. Being a virgin though, she might be shy about being on top and would probably prefer you being in control, so the missionary might be better.
Good luck and let us know how it goes!