Well since you want to play online there is a ethernet port that you can plug your internet into, OR if you have a wireless connection you have to buy this little gadget http://www.amazon.co.uk/Microsoft-Xb...5013621&sr=8-1
Kind of pricey but it saves alot of mess of the wires and all but maybe you could work it out.
You also need to buy xbox live membership which is also kind of expensive but soo worth it imho. You can order it by credit card straight from the system or buy the time cards. here is one for 12 months..they also sell a 3 month and i think 6 month card http://www.amazon.co.uk/Xbox-Live-mo...5013688&sr=1-1
and lastly you may need an extra controller if you have siblings or friends you want to play with http://www.amazon.co.uk/Microsoft-Xb...5013766&sr=1-1
and Yea it will work perfectly fine on your TV. and you save money by not needing the HDMI output cables for HDTVs. Lucky you.
Goodluck I hope this helped