how do I reserve a date/time to tour sistine chapel
It's part of the Vatican Museum and is not handled separately. See #6 on Ron In Rome's excellent list of tips on visiting the Vatican Museum here: http://www.roninrome.com/%20sites-and-attractions/20-tips-on-visiting-the-vatican-museums
I would also recommend you download Rick's audio tour of the Sistine chapel. I did that last year and went to the back of the chapel where there is a bench and listened to it and it really added to the experience.
As far as I know you are not allowed to "tour" the Sistine Chapel. You can take tours that include the chapel but they give you all the information about the artwork and history before entering. You are not supposed to talk while inside the chapel, this applies to guides as well as everyone else. You can reserve a timed tour of the museums and chapel through the vatican website. It takes about 2 hours to do the tour and the last room you see is the chapel. After that you can use the "tour door" to go straight into the basilica if you wish. http://biglietteriamusei.vatican.va/musei/tickets/do?weblang=en&do Donna