Your scrapyard replacement works like a dream, yes? This is three years newer than a whole lot of stuff that is in or on your car? Are you going to rebuild or replace every component on your car that is older than 17 years before you make the big trip?
No, of course not. Electrical components can fail suddenly after working fine for years, but equally they can go on giving good service too.
There are two tools an old car enthusiast needs, a cell phone and membership of a recovery scheme.
Try and develop a relaxed attitude. Life's too short to worry like this!