My sister and I gave a certificate for the ride-a-long experience to my Dad for father's day and he used it 3 weeks ago when all of us were down at Disney. It was a phenomenal experience. We got there on Wednesday at 1 PM and, as it turns out, there was absolutely no other customers there. Because of that, they allowed us extra time for the photos. Basically, the experience consisted of my Dad putting on the uniform (tip -- go 1-2 sizes larger than what you normally wear) and the helmet and then filling in a few fields on the computer. They then put him in the car along with the driver and a woman came out and quickly snapped his photo in the car.
The driver then zoomed off and did 3 laps around the track at 140-150 mph. Afterwards, they pulled in and we were allowed some more photos of my Dad and the driver. After that, they gave us a plaque that we had bought signifying the experience. It's a nice plaque with his picture and card indicating that he did the ride-a-long experience. My dad said that that was fun and an experience that he would never forget. He's a huge NASCAR fan and, at 70 year old, he never thought that he would be able to experience that and now he has.
As for the total amount of time spent -- as I mentioned, we were literally the only customers there (another family came in after we were done and were shopping for souveniers but that was it) so we got to take our time. But, even so, it was approximately 20-30 minutes total for the time of him putting on the uniform, getting in the car, racing around the track and getting photos taken afterwards. Obviously, if you don't luck out the way we did and you happen to get there on a day when others are there, the wait time will be longer (the ride-a-long experience is first-come/first-serve with no reservations taken for it).
Not the cheapest thing in the world (what at Disney is?) but was worth every penny just to see the silly grin on my Dad's face. The people at the Richard Petty Experience were wonderful and I can't recommend it highly enough for people who love racing or know someone who does.