Cinelli Handlebar / Stem Issue
I have just come into possession of a bicycle from my grandfather Bill who was a bike enthusiast. It has Cinelli brand Colorado handlebars, and I was tinkering with them, trying to change their position a little bit, removing the bold at the bottom on the stem, thinking it would loosen the handlebars...well, it did not loosen them. As the bike hadn't been used in years, I was not surprised I encountered a bit of resistance as I screwed the bolt back in...but upon closer inspection, to my horror, I realize I have stripped the threads of the bolt, and perhaps threads the underside interior of the stem.
So, my questions are two: 1) what purpose does this bolt serve if I cannot loosen the handlebars after loosening it and 2) is there any way to replace the semi-stripped bolt (& the one inside the stem)?