There is a Ford Special Service Tool which can be used to remove roller finger followers (RFF) without removing the camshaft. With the RFF removed, I'm pretty sure that you can change the lifter. I'll double check and get back with the tool number.
The tool hooks around the tube of the camshaft and has a finger which pushes down the valve spring. This unloads the RFF for removal. I've also heard of people popping them in/out with a screw driver but you run the risk of scratching/damaging things.
