1999 Mercury Mystique GS 4 Cylinder 2.0L Engine 159k miles?

Changed my timing belt just a few years ago. Recently the lifters began rattling badly at idle & low speeds, sounds like crap. My question is how can i fix this problem or get any info on how to replace lifters for my engine. They don't have instructions on lifters in my 26170 Chilton book. Please help