I think Nordic is spot on.
You have some good idea, and not everyone try to design their own car.
Even with gimp it's possible to accheive good things, but there is just less freedom and harder to get the outcome you might want.
Just start small and try to perfect individual areas instead of trying to do too much.
Like the interior shot, try to spend some time on the steering wheel and make sure it's actually round, or the center console, gps actually covers over the old parts on the dash.
Everyone can copy and paste, but it's how well you can integrate the parts and make it fit perfectly/ looking realistic is what sets people/ chop ranking apart.
Dont be lazy, cut corners, make sure it's perfect before moving to the next part.
Good luck
