Alright a few things:
There
is an easy mode. This is probably closest to "normal" on the GBA versions, so don't completely freak out.
I'm just happy that
finally we've got a difficult Fire Emblem game --if you want to. IntSys seems to finally have come to an accomodation between pleasing hardcore fans from the SFC era like myself, while still keeping the game "accessible" to people new to the series. Maniac makes me happy. But lord is it hard. (That's a good thing.)
No, you can't change the difficultly level midway through the game. You'd have to start over. The game'll let you know if you're above or below your skill level within about four chapters in. (About an hour).
As for Blacksmithing and Skills and everything else that's new, there's an optional tutorial that shows you how it works. You can skip over it if you like but it's in there so it'll be explained to you. Also, you can just try it out and see. Skills are really self explanitory. Blacksmithing is fun, if expensive. Remember you can press the X button to get a "description" of the item you're looking at too.
As for it being the Game of the Year, I'd definately vote so, and I adore RE4. Heh.
I hope this helps, and ensures a few more Fire Emblem: Path of Radiance purchases. Heh.