i'd say ditch the tripod & hire a faster lens for the weekend
the tripod will be too restrictive!
you need something like a Nikon AF-S DX 17-55mm f/2.8 G IF-ED
available to hire from here-
http://www.lensesforhire.co.uk/nikon...if-ed-58-p.asp
you can hire for a week which should give you some time to learn how to get the best out of it.
the only thing you can do that will help you is practice!
practice all the time you can then when not practicing have a browse around the net at professional photographers sites so you can get a feel of the kinda shots people want
you only get one crack at their special day so you want to do it as best you can
i got a buddy who's a very good wedding photograher . have a nose through some of his stuff
http://www.grahamnixon.co.uk/slideshow-lorna-dan.html
other weddings are clickable from the bottom bar