The body breaks down Carbohydrates into simple sugar as part of the digestion process, so Carbohydrates are in effect 'Sugars'. You should aim to reduce ALL sugar intake whether it be directly mentioned on food labels or hidden somewhere in the description.
Many Low Fat foods are loaded with sugar to compensate for the lack of taste.
Gi and GL are basically the same thing, it's a relative measurement as to how the average human's blood glucose level will rise in relationship to absolute pure sugar (Glucose) which has a Gi rating of 100. This means that Gi ratings below 30 are generally preferential to those higher than 70.
Publications are readily available on the internet and even here on this site. A good book on the subject that comes to mind is one called 'Carbs and Cals' which itemised a whole range of items and shows each item as a portion.
This is where the GL comes into being, as its actually a Gi based item but simplified to being a realistic portion size. If you look up the Gi for instant of Mellon you will usually find it rated above 70 but in the GL rating system (which I believe to be the better option) it's considered as 'Low' and can be freely eaten.
Hope this info helps - All the best with controlling your diabetes.
