Here is the chart that was mentioned by both hydrohoki and pigsforlife.
http://www.guineapigcages.com/forum/diet-nutrition/22156-everything-you-need-know-about-cavys-diet-read-me-nutrition-charts-info.html Reviewing the information on
Guinea Lynx :: A Medical and Care Guide for Your Guinea Pig is also a good idea.
Most of the time, basic questions can be answered by doing a forum search or looking through prior threads in each section. Information about vitamin C has been asked and answered multiple times.