The headset is the component that the fork and stem are assembled in. Problem Solver's makes a headset reducer from 1 1/4" to 1 1/8" which is the standard used today. If the heaset goes out finding a 1 1/4" is not as easy as a 1 1/8". Of course if the headset does go out then your fork and stem become wall art.
Look I am not trying to beat on you or argue just point out some stuff. You said you wanted to obe educated, and you wanted opinion's I gave you mine. I do not see a need for a bunch of needles hostility.
If you want to learn fine I can help. I am not bashing you on your MTB ignorance, because we all have ignorance on bikes. Cool?
By the way I still use top mount thumb shifter's as you have on that bike. Your before and after pic's are great nice job on cleaning it up!