You have to get to lions arch to get to eye of the north but if you have night fall or factions you have to get somewhere else
No it does not. Reason for me saying: I bought GW GotY before EotN ever came out.
You will be able to. But your game will crash in certain areas (Mainly Asuran territory in EoTN and some dungeons)
You enter Eye of the North in guild wars by: 1. Purchasing the add on, 2. Leveling up to level 20 on your desired character and 3. Visiting one of the major cities in each campaign (if you achieve level 20 a popup will tell you who to talk to) If you have Prophecies, go to Lions Arch and thalk to a guy there and he gives u a quest that is the beginning of EotN. You have to have the EotN game though.
Max armor can be obtained in towns and outposts throughout the different campaigns. In Factions the earliest place is Kaining centre (can't spell), Nightfall is Consulate docks, and i think prophecies is the southern shiverpeaks. You can also get it in the first outpost of eotn