Vince Gil does not drive a car and has never had a driver's license. They did teach him to drive enough to get what they needed for the film, and he was otherwise driving under a permit. According to Vince, "I didn't really learn how to to drive properly, but it taught me enough to be a better pedestrian". According to Vince, Grant Page was also definitely present in the car at all times, crouched down behind the driver's seat giving instructions.
As for the shot of the foot pedal, I don't know - but it is certainly a shot that would have been done in a stationary car, and possibly done at a different time to the rest of the filming (and therefore unlikely to be Vince - more likely to have been someone that was generally around more of the time, such as Murray or Grant). Noting that they destroyed the Monaro, it would also follow that they may have determined the requirement for this shot after that car was gone, lending credibility to the fact that it might have been done in a different car. Who would ever notice!