@Tom_MN
If your schedule allows, I'd recommend giving yourself a full day to travel Berlin-Wittenberg and back, and include a few hours walking through town and visiting a number of the sites in Lutherstadt Wittenberg (tourist info, in English).
To get a feel for some of the Luther sites, I'd say:
- Lutherdenkmal, Melanchthondenkmal : Luther & Melanchthon memorials at the town's market square
- Lutherhaus : Luther House
- Melanchthonhaus : Melanchthon House
- Schlosskirche : Castle Church
- Stadtkirche St. Marien : St. Mary’s Town Church.
The latter four are part of the town's inscription as a UNESCO World Heritage Site.
Side note: a number of years ago, I appreciated attending the sunrise service in English at the Protestant ("evangelisch") Castle Church on 31 October which is Reformation Day and a holiday in a number of the northern German states.