If you want it to look like new (which I wouldn't ... I like the age showing) I'd check with Dave Martell at Japanese Knife Sharpening and see if he'd like to take it on.
If you want to keep the battle scars but make it useful, it probably won't be too much work. I'm guessing it's carbon steel, and not terribly hard, so it should be pretty easy to sharpen and work on. If you already have a full set of water stones you're pretty much ready to go. The first step would be removing the active rust (anything red or brown) with Barkeeper's Friend and a scouring pad. This will take off all the patina, too, but it will come back. And don't forget to take care of the wood with some conditioner, like the beeswax / mineral oil blends used for cutting boards.
After that it's just going to be about repairing edge damage with your coarsest stone, putting on a new edge with a medium stone, and then polishing with finer stones, if you like. None of us can tell you how fine a grit to sharpen to. That's going to depend on what you like, and on what the steel will take. If it's a soft or coarse-grained steel, going much beyond 2000 grit will be pointless. Depending on how you use the knife, and how you like to cut, you may not want to go past a toothy 1000 grit.
FWIW I go to 1000 with my German chef's knife and anything I use for butchering, boning, or ripping open packages. My gyuto and slicing knife I take to 6000–10000. This gives a polished edge similar to a straight razor, but doesn't really make sense for a butchering knife like this.
I believe one traditional use of scimitars is butchering meat that's hanging from the ceiling. The curved blade makes it useful when cutting overhead. Another use is slaying your enemies when they're on foot and you're on a horse.
