This is not an easy task that you have been asked to perform. As you state the current good practice is always being updated. You really need to be experienced in the subject and be well read around the subject. It is quite different from the quality and operations in other chemical / manufacturing facilities.
Firstly you need to gain an undstanding the intent of cGMP (and its associated GLP, GCP etc).
I would point you at websites for the FDA and PDA (Parental Drug Association). Then various magazines that are available.
The basic rule is that the FDA (and the other national bodies) assume that every one is a crook and if you can lie / forge something you will.