Blackpowder shooting is great fun. While I don't do nearly as much of it as I'd like, I am comfortable with firing them. I will warn you that you can expect misfires more often with muzzleloaders than with regular firearms, so be sure you're safe when that happens. Keep the muzzle pointed down range, give the rifle a long wait before doing anything, try another priming charge, etc.
While I haven't had the chance to try it, Cabella's sells a kit that includes an adapter and a CO2 cartridge that will blow the charge out in the event of a misfire. The alternative to this is a long soak of the barrel in the bathtub to deactivate the powder followed by using a screw attachment on a rod to pull the bullet out and clear the barrel
My Dad has had to do that a couple of times over the years, its not a fun thing to deal with.