Glad it was a simple fix! If the fuse blows again, I THINK this is one of the very rare occasions that this is true that MB actually allows you to increase the amperage of the fuse. The fan motors may increase their current draw with age/use. That happened to me; the fuse would blow every few months and I went from a 15-amp fuse to a 20 with no further problems. If I'm not mistaken, Arthur has posted on this very issue in recent months.
You are generous indeed to buy a very nice car for your ex. You are right about them being overbuilt. In my very limited experience, most systems are just enough different from what I'm used to in American cars that they are not particularly intuitive, but there IS a rationale for every engineering decision made. You and I might not agree with that decision, however ...
you are a real font of wisdom. I ALWAYS learn something new when I read one of your posts!