I did some of the smaller parts....
After about 5 years of flying, the cockpit coaming on my -4 was rather beat up. Rather than repainting this surface, I used a 3M film. It has proven much tougher than the orginal paint. It has been in place for 5 years and still looks great. Similarly, I used film on some interior components to avoid the hassle of painting. It worked great. Doing a whole plane would be a big job, but certainly is acheivable. You can get good weight estimates from the manufacturere, but I would expect it to be similar. It lays down over rivets well (you can't tell it's not paint), but I agree with a previous poster that it may be easier to apply second/third colors with this system due to the difficulty in laying film on complex geometries like the flap brace, or the exposed portion of the rear spar of the horizontal stablizer.