What a great payment. Nice rifle.
I'm guessing that this is your first muzzle loader. Sorry if I'm telling you things you already know.
Ditto on checking it out first, although you can do most of it yourself. Find out if its loaded by the ramrod method, then get a cleaning jag, and work on the barrel, first with a water/detergent/alcohol mix, then regular gun oil (I use break-free). Expect some rust to come out on the patch at first.
Get a nipple wrench, pull the nipple, and inspect the threads. It they're trashed, don't shoot it. BTW, that doesn't ruin the gun, because you can replace the thimble. Remove the screw on the side of the thimble, and clean out the passage.
Now get information. The Lyman books is great. CVA has a very good generic manual at http://www.cva.com/pdfs/Side.pdf
. Find a local muzzle loading/reenactment group.
There are a bunch of places the you can find parts and supplies, including Midway, Dixie Gun Works, and Track of the Wolf.
Looks like the max recommended load is 80 gr FFg with a .440 patched round ball. I'd start with a 50-60 gr load, and play until you find the rifles sweet spot. You can also use FFFg, just be sure to reduce the load by 20%.
Bunch more info can be passed on, but I'm getting long-winded as is. Get info, and have fun with it.