i'm pretty sure the stealth and chrome line packs are purely DLC, so i'm sure they will be available to purchase seperately, for a small fee (since EB games is doing the stealth pack with the standard edition of the game). also those cars will still be in the game, i'm just guessing that with the addition car packs you simply get those cars straight away and you don't have to earn/buy them, but i really don't know. it could simply be that they aren't in the game and the car pack simply adds them into the game but you don't get them for free.
and as someone else replied to you, according to a reviewer with the actual game, standard cars wheels cannot be changed. no speculating involved here. i think maybe you should go and change your tampon.
and yes, there will be 2 player split screen, just with limited views available (seems to just be bumper and above car views, and can't save replays)