An MMORPG is quite an undertaking :shock:
I suggest you start writing things down first. Write down everything you think is needed for the game. What kind of engine (2D/3D), editors, script engines, graphics, IA (if needed (npc's?)). Don't take this too lightly though, look at other mmorpgs for reference.

Then for every item specified above, write more detailed what is has to do, what it's requires and how long you think it would take to realize and more important if you can realize it. For example, a tile-editor should be no problem, but how about pathfinding?

Once you have finished this 'blueprint' (and still think you can do all the things you wrote down) you can start thinking about programming.