Heh, Up, Up and Away is actually a cinch if you don't go barging in, like I did the first few tries and take your time. I used an AK47 (since I'm at Hitman level with it) and just took my time picking guys off.
That seems to be the best advice for most of the non-driving missions: slow down, and pick off every enemy you see.
BIG SPOILER!!!! Being able to drive through a graphically updated Liberty City instead of doing just one mission would have been the markout moment of markout moments.
As far as Millie, just try her house everyday sometime after 17:00 or so. That's usually when she gets home, it looks like.