Your wife is right. You may be the best driver in your state, but that means nobody else is. The design of the rest of the car won't protect you. Just for fun, sit in the passenger seat and smack your head on the dash board as hard as you can. Then realize that the impact was only 1/4 what you'd experience in a 40 mph impact. Look at the chrome mirror, the stering wheel, and all the hard surfaces that can hurt you.
The job isn't that hard and, as you'll see from the threads on this site, it can be done beautifully. After brakes, they're the next necessity.
Ray
'68 280SL 4-spd Coupe