The bore is in pretty nasty shape.
A lead lap and a LOT of work might smooth it up a bit.
Anew nipple is recommended, of course.
Should be fun.
If the barrel is not smoothed considerably, the bore will foul badly - spoiling the fun of shooting it.
Use VERY wet patches.
Oil like Neetsfoot Oil for hunting, while a water based lube for plinking will work and shoot more cleanly as well0

I use winter windshield washer fluid with a bit of Neetsfoot Oil added, for target shooting with my ML's - about 2 ounce oil per quart. This mix shoots well. You do not need, nor want soap in the mix.