I'll add that getting tickets online is confusing, google gets you tickets to the church, which are free, but you need an extra ticket for the museum and ideally you want the guided tour or the audioguide, and those do sell out.
the church where the battle ended
some original frescos were found under the plaster
The museum had lots of artifacts, most of which were acquired by Phil Collins and donated to the museum:
When doing both the guided tour and audioguide, plus the museum, it took close to 3H. I still had to watch the movie after the fact to get the fuller story.
They also had a quick history lesson:
I'd say it's probably somewhat skippable, and somewhat out of town, but it was open when other things had already closed, so I went.