We've never spent the night in Le Mans. Once we ate in a boulangerie and once we got takeout from a small street lined with restaurants but I don't think we picked the best restaurant. So no dining advice from us.
We were blown away by the Roman wall, what remains of it. It's spectacular and amazing. It is a high brick wall in colorful patterns. Those Romans built to last.
The old city on top of the bluff is chock-full of half-timbered buildings.
The cathedral has a chapel whose ceiling shows angels playing musical instruments. Next to one of the cathedral doors is a menhir, an interesting juxtaposition.
There are illuminations at night on many of the buildings in the central area. They are not as spectacular as the illuminations at Chartres but are well worth seeing if they are still happening when you will be there.
We visited the Museum of Tessé to see the temporary exhibition on the Roman era in Le Mans.
I know the 24 hours is the major attraction in Le Mans, but I can't tell you a thing about it. Seeing the old city center and wandering through the shopping area on the other side of the river were entertaining enough for us.