How to wipe a ROM'd Incredible

My Incredible is rooted and I've installed CM7. My daughter used it for a while until I was able to score a Moto E 2015 on the cheap. My daughter took pictures, installed stuff, etc. I'd like to remove all of that but leave the 20 GB of music in place on the SD card.

What's the best way of returning it to a stock CM7 device without deleting off the music?

TIA, CheapDad