Sennheiser pc 350 + MacBook = ???

Hello, my name is Shane. I'm currently on my second deployment in Iraq, and I'm having some issues.

I went Mac in february of '08, and haven't looked back. Well When I got sent over here, I needed a headset for Skype, iChat, and other various applications. I asked my wife to send out a headset to me. She asked some questions online, and came up with the Sennheiser pc 350. I know nothing about this stuff, honestly, but she said that the website said they were Skype, and Mac compatible. All the reviews said audio and microphone quality was great, etc. Then I found out the price (after I already got them), and I am told they are overkill for listening to dvd's, music, and skyping, but I have them now and the sound quality is pretty decent.

That brings me to the part I do not understand. The microphone; how does this work? I went through all my settings, used search engine after search engine, and can't make heads or tails of the tech talk. Do I need a sound card to make the headset mic work? If so, what would be the best way to go? I'm looking for something that will make the headset mic work, and bring out the best quality sound from my music, and movies (I love my movies, and music!).

Also, could someone explain to me why I can't just plug into my mic/line-in port, and have a working mic?

Thanks,
Shane

I'm sorry, I guess I posted this question in the wrong place? Please move this to wherever it needs to go to get my question answered.

I need headphone ability because I share a room the size of most bathrooms, with two other guys, and the only way to keep the peace, is by not sharing our music and movie noise. I need a mic close to my face so that I'm not bothering my roommates by having to talk loud enough for the internal mic to capture over all the ambient noise. I already have the headset, now I am looking for a good-great quality product to improve the sound to the headphones, and enable the mic to work.
Help, please?