Hey B2

The trick to Ave Maria (from experience) is NOT to be Pavarotti. Be yourself, most couples want a more contemporary feel to their wedding music, and if you over do the operatic vocals it will sound too unnatural. Be yourself, you will do fine.

As far as the hardest song, while SSB is difficult, you can put it in the right key for you and be okay.

A hard one for me is Paul Davis' "I Go Crazy." Some really low stuff in there.