The face-stuff isn't so bad. I've brought three characters into ME3 so far (all from ME1), and only the first character had to be tweaked. Though that was because she was the only one pre-face patch.
And you'll want to kind of get on it, Synk; supposedly the Extended Cut DLC (the ending stuff) is getting pulled off the market at the end of the month.
edit: And the best way to do it is to run the whole game and beat it, then go back in and load the Citadel DLC and play that last.