Who are you booking the trackday with ? Most trackday organisers can arrange for an instructor if you want one, its at an extra cost of course, ask them. I used to do a lot of track days with the group b car club and there was always a couple of people to show the newbies the ropes, spme do beginner sessions as well where you can follower an instructor for a few laps just to get a feel for the right lines etc....