Gran Turismo 5 Prologue Question?

[sega4life]

I got GT5p today at Blockbuster for $19.99 on sale..

But I have not opened it yet..

I have it in my hand debating on whether I should return it or keep it..

I know $19.99 is a great price, but at the same time the game/demo doesn't really have allot to it as I thought it might..

I was on PSN Store with my PC and I can not find any addons for it, besides the 3 car update..

I remember someone telling me that they added like 20 cars and such, but I can not find this add-on, am I missing something or was it just a false statement?

Also the last update for the game was a looooong time ago, do people still play this game online?

Should I take it back for a diffrent game on sale?