A burner wouldn't spark strongly enough to light the gas.

Replacement of these burners is very easy. You just twist the burner counterclockwise a quarter turn and pull it out. (You may need a big wrench if the range is very old.) Once out, just pull the two wires off and push them onto the new burner. Crimp them on with pliers if they're loose -- mine were. Twist the burner back on.
If the gasket under the burner has disintegrated, don't worry about it. They don't offer replacements for them because they're not necessary as a safety feature. They were designed to keep overspills from running under the cooktop, but the ridge around the hole is likely higher than you'd ever need.