I wasted a whole lotta ammo too, but with some practice you'll probably get used to it. It took me a while to master MGS2's pressure sensitive aspect of aiming and firing too.
As for sneaking, I found that I had to rely on first-person view and crouching a lot when not using sonar and motion detectors. You definitely can't sneak around the same way in 1 and 2, using walls and crevices to hide yourself. I got semi-nailed early in the game but never again after I decided every guard must be tranquilized before I go about my own business. The AI was nowhere nearly as smart as in 2 during the clearing phase. I'd hide under a log and shoot them at the feet, they'd be firing at me with automatic weapons and never hit me.
I still think MGS2 looks and plays more slick than 3. Backpack management and manual switch of camo are the 2 worst and useless new features in MGS3. If they wanted to make the game more realistic, how about making taking a leak part of the experience?
I got bored with FM4 about halfway into it - the story develops at a slow pace, with the combat at an even slower pace that seems to take forever. MKD tided me over until I got AC5.