Raming other players in a race is frowned upon in the GT community. Hence why they voiced it enough to have PD fix it. The "quick" fix was to give the rammer a time penalty (car is slowed for 10 sec or so) however that still didnt stop the rammers. So PD made it so if a car is identified as going to ram another car then that users car or the opponent will become a "ghost".
This will most likely change when GT5 drops as it now has damage and that will be a huge deterrent for rammers.
All i can say to you is dont get in the habit of ramming people in GT as it will quickly get you put to the ignore list of ALOT of GT players and you may end up finding yourself playing alone or with other rammers (which may suit how you intend to play the game). If you really want to ram i would suggest you get Burnout or the next Need for Speed game.
As for the other questions.. there is no lobby system in GT5:P so you cant pick a race/car/laps/etc.. its all pre defined by PD with the events they post up monthly. There are PP (Performance Point) requirements for each of the races to keep it competitive.
GT5 if you have already read up about will have a lobby system which supports 32 players (16 on tract and 16 spectacting), you will be able to pick the tracks, damage, PP, laps, etc.. you can make tournaments, Race teams and more. GT5 will have a huge info drop at next months game show.
