Visiting St. Petersburg - guides?

Hello fellow expats. I'm planning a trip to St. Petersburg around September 8th or 9th, for three days... I would love to find a knowledgeable guide, preferably a local, who can tour us around. Time will be limited and I want to make sure we have a great experience. Any suggestions?
Also, any tips on great restaurants, bars, and non-tourist experiences are greatly appreciated.
Thank you for your help!