Hello from Auburn, CA. New here with questions

I have been asked to perform (solo) a song for my daughter’s wedding and I’d like to play some harmonica along with guitar and vocals. I am a pro level guitar player but have never played harp.
I have an old Hohner Marine Band in D that has never been played and I’m wondering if I should just use it or if I should upgrade. I don’t mind spending a few bucks and I very likely will continue to play the harp with my band which plays mostly classic rock. Thoughts?