I would have been 9-10. That put me doing major wrenching on my banana bike (ever change rims to get the right gear ratio by undoing and re-installing all the spokes)? Traded something, maybe a slot car for the Tyco raceway, for a set of those handlebars with the big loops on the top before they headed back to the rider. Hard to describe, but really set my bike apart.
I had probably learned that waxing my Dad's '68 C10 really made it look better, and might have been changing oil around then, too. Kept getting in big trouble for raiding Dad's tool box. He took care of that one Christmas.
SSOW