Yes, I would happily do so. This assumes, of course, that state law authorized me to perform wedding ceremonies and did not prohibit gay couples from marrying. Can anyone put together an argument why I shouldn’t do so?*
*Incidentally, don’t worry about being labelled a bigot if you take the position I shouldn’t do so. You aren’t a bigot if gay marriage isn’t your cup of tea. Indeed, I can think of several solid reason why I shouldn’t perform such a ceremony.