How hard are MTTs?

[Atropos]

Hey folks,
this may seem like a stupid question, maybe it is. My main game is grinding the 100-200$ buyin NL 6-max games, I have some STT experience under my belt too. Considering that I:
a) Know how to win playing NL
b) Know the basics of blind stealing/blind defense from STT
c) Know how to play a big stack, exploit the bubble
d) Am rather too aggressive than too passive, which seems to be suited for tournament play

How hard would it be to learn decent tournament play? I dont want to become a MTT-specialist, NL cash games should stay my main game. But I want to be able to play the large (big fields) tournaments like the 215s on Party + Stars every weekend + the occasional Party Poker Million etc...

I want to be good enough to be marginally +EV and see them rather as some kind of lottery chasing the big wins, not a way of earning money, however I dont want to throw money out of the window.

How hard is it to accomplish that? Do I need to play weeks consisting only of endless MTTs to get enough experience? Considering my time is very limited at the moment (school and other stuff) would it be better to wait 3-4 month and just grind for money until then?