It can be a tough one, although really only on Hard. Black Ops is a breeze (just shoot anything that moves or blows up with a grenade) and Easy/Normal both have more than enough Health Packs. Little trick I found was to deal with the entire final room from within the tunnel that leads to it. With some good shooting and a little luck you can finish it off without even leaving the tunnel, thus giving you a safe place to run away to if needed, since the baddies don't follow you up those stairs.
As for the lack of a boss fight, that was because the boss was being saved for a possible Black 2 as far as I know. If/when that game ever hits the market is anyone's guess, but hopefully sooner rather than later. And it better have multiplayer, heh.
"Have you seen the posts around this board. You HAVE to act like a child to get attention around here." - AlabamaMan79