Not easy questions to answer simply, except the last.
Camcorder mics are usually poor and can suffer from picking up camcorder motor noise. Any decent (50+ quid) mic will be better.
As for the other stuff, well depends on a gadzillion factors really and I am certainly no sound expert and no wedding vidder.
Off the top of my head I would say a decent shotgun (meaning expensive ) mic from six to twelve feet away pointed accurately would do the job.
I dont know what the deal is with stands / lapel mics ect at weddings, I have always presumed that you just have to 'fit in'