The VIN does not inherently contain the car's options. That being said, GM knows and documents the options for each car's serial number/production sequence (which is contained in the VIN). So you need a cross reference between the serial number and the options (RPO). That is now hard to find online.
GM's VIN decoding card can be found here:
http://service.gm.com/dealerworld/vincards/
That will give you the basic data (year, engine, transmission, production plant, etc.) but not the options on the car (e.g. sunroof).
There was a site called CompNine that had an online VIN decoder with all you want and more. Unfortunately, they just closed their doors.