The first problem you will encounter with Diplomacy is the rules. These are split, by Avalon Hill, into fourteen sections. Unfortunately, the first section is approximately 5.5 lines, and the second section is 11 pages, less 5.5 lines. Play a sample game or twenty, until you understand the rules. So the cover of the rules tells us.
Diplomacy is a game of skill and cunning negotiations.
Chance plays no part. The seven Great Powers are England, Russia, Turkey, Austria, Italy, France and Germany. Different people will tell you different things about which powers are better. However, take note that there is a reason why the person who is assigned Italy will look glum for a while. These can be land, sea, or coastal.