I really wonder why I bother checking here.
SSP you've been on this forum long enough to know that, anyone seeking advise concerning a religious service or a minority ethic community's customs, risks getting stick from those who are completely intolerant of other people's beliefs and lifestyles.
I don't believe for a minute you are that naive. You might well be disappointed, but I don't expect you to be surprised.
Whatever you decide to wear, I hope you enjoy your Sikh wedding – I only wish I had the opportunity to go to one. And certainly experiencing other cultures and traditions will broaden your horizons far beyond those of narrow minded and insular bigots. Have a good one 8)