As far as I know you can only race single player races offline and no seasons of any kind. If you wish to join a league you should go and play online where the real competition is.
I can't help you with the F9 dialogue, but you can chance the tires when you press F12 then you can change the tires, pressures etc with the arrow keys.
Nope I have a 512mb Vid card with DDR 3. Only thing that is a bit sucky atm is my CPU, thats a P4 2.6. Well I will give it a go and see what comes out of it