What do you need to do to play online in the car ? Who offers mobile internet? and would i need a router in the car ? Any info would be great!

you might be able to do it on a 3G network however keep in mind that this will have horrible pings and you might lag out of games. you might want to check this out:

http://www.evdoinfo.com/content/view/2455/64/

It will allow you to use your PS3 in the car as well as anything else you want to have internet. Good luck