I would follow the advice of your stoves manual. Burning coal is nothing like burning wood.
You don't need a big investment in a coal stove to start out. Today I saw on Craiglist a Warm Morning stove and a couple hundred pounds of coal for free
in the Boston area. While free stoves are not the norm of course you can find a good used coal stove for well under $500. I paid $100 for my coal stove and it was the best investment I ever made.
If you will tell us what part of the US you are in someone on the board may very well be able to help you find a good used coal stove near you.