Scott,
I've got a Lindsey with the foot control and love it. But you need to know you are on a slippery slope for tool acquisition. Most everyone here already understands that. You will need a good quality air compressor and maybe a filter for it. Pneumatic engravers don't like oil or moisture that most compressors can put out. If you' re only going to engrave muzzle loaders (brass and soft steel) you won't need carbide graver tips (they're brittle and will typically break the tips until you learn to handle them). Stick with high speed steel, you can sharpen them on stones you probably already have. Get several extra so you won't have to keep sharpening the same 2 or 3 that come with the engraver. You will DEFINITELY need the Lindsey sharpening system, it's the secret to getting the same angles every time in order to engrave. Get the Universal, it's all you'll need. You will also need a pocket microscope, cheap at HARBOR FREIGHT. You'll need it to check the tips as you shape them and to see when you need to resharpen those tiny heels on the engraver. Next you'll need some type of vice that you can easily and smoothly rotate 360 degrees while you are engraving. Most engravers use a ball vice, the bigger the better. Finally you will probably need some type of optivisor to see your work. Check out the websit called Engravers Cafe, look for the button "Tips Archive" and look for Tool List for Beginners. This web site has everything you'll need to get started into engraving, ...except for one thing.... You really need to get someone to give you at least a short lesson(s) on sharpening and using the Lindsey engraver. I'm not saying you can't figure it out on your own, but it will definitely increase your learning curve.
Best of luck. Watch out you might get bitten by this bug.