Hello C3PO
FS One is regarded to be currently the 'best' F1 mod - although it depends really on what you're looking for in a mod.
You need the latest version to play online - 1.4
IIRC you need to dl 1.3 then the 1.4 update. You can do that at rFactor Central
HEREor from the modders website directly
HEREYou have to either use the default 2006 skins as the 2007 skinpack isn't finished yet, or download the ProF1tr 2007 skinpack and use that - but there are physics changes in that pack, so it won't be as realistic and you then can't race on servers not running it.
You can also download the FS One trackpack - which currently has about 6 finished tracks on it - the rest are WiP.
If you don't like to fiddle with set-ups you are unlikely to get on well with this mod. Just to get to the chequered flag without blowing your engine or brakes needs some fiddling. Some of the settings have been improved in the 1.4 update, so it may not be as critical now.
Good luck and have fun