How much of a scenario do you ought to know (when you start playing it)?

[BigDuke66]

Play it blind, but set yourself a "stage".
What I mean and what I usually do is read wiki article or another good source covering this battle, and read it up to the point where the detailed description of the battle starts. From that point on I play. That in combination with the scenario description is enough to bring you more or less on the same level of knowledge that the commanders had back then.