-hacking just means someone is cheating. you can't *always* tell if someone is cheating or not. then there are other times where it's blatantly obvious. but there are some times where someone is yelling "hacker!", yet the person is just really good.
-there are personalized skins you can use, but ONLY if the server has them installed as well. most servers will just have the default skins. as for binds, yes, you can bind, say, the letter "H" to say "good shot" by typing this in your config.cfg file: bind "H" "say good shot!"
-you can go to websites that host maps for CS if you don't have it already, to make the game load faster. but most of the servers out there play the default maps, which you already have. so if it's loading slow, it will more than likely always be slow.
-well, there's this thing called "Friends". it's kinda like xfire, but built within Steam. if you have buddies on that Friends list, then yes, you can PM them, otherwise, no, you can't PM people that you're playing with unless they are on your Friends list.
-typekill and spawnkill are kinda two different things in CS. typekill, i guess, can be acheived by dropping the console, "~" button, then typing "kill" and hitting enter - you instantly die. spawnkill is on certain maps where as soon as you spawn, someone from the other team has a line of sight on you, and instantly kills you. you can also world kill, which means you can fall from a high building or go out of the maps bounds and die instantly
-i don't know of a way you can protect your account. just pray no one randomly picks your cd key with a generator. Steam has made some adjustments for this situation though. i'm pretty sure that if someone does steal it, you're allowed to have 2-3 active computers with the same key at the same time. but if you can't log on for some reason, Steam support, i heard, is pretty good about getting your account all straightened out.
Let us know if you have more questions.