have you seen the thred "help with diy wedding" ?
i had a friend shoot the wedding after 1 months practice with my eos 350d
he took about 400 pics, we got 180 ish good shots and 40 or so really good ones. we are really happy with the results, and havent even tried to photoshop them yet.
however a pro did come too, by chanch a photo journalist friend.
her shots are better, so if your looking for sharp perfection you are really going to have to bite the bullet and hire a pro.
if you do get a learner then make sure they can boss guests about, arrange people, handle the awarked unkle who dosent like having his photo taken, has a backup if it rains. knowes some wedding poses for you to stand in, and little tricks like putting your hand on the brides back, not all the way round, to avoid odd finguers poking out.
a book on wedding photography will help.
students are ok as long as they can stay focused (haha)
watching out for signs like the champine comming out as the que for the speech. etc..
you dont want to be following a half harted student about saying "did you get a shot of aunty Doris yet?"
youll have enough to do.
i hope this helps, good luck on your wedding day.