I do weddings as part of my photography business, and I never recommend doing a friends wedding, that is unless you don't mind loosing a friend. Wedding can be the demise of a good friendship..
That said, if your going to use LF gear, do as Ted said, then grab either a 35mm or a compact MF body and shoot lots of film.. or digital depending on what you have.. and make sure you are up to snuff on lighting techniques.
Good Luck.
Dave
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