Working with Photoshop layers in FCP X is pretty simple. When you import a layered .psd file, it will import as a Compound Clip, all the layers are there in tact. Use as you would any Compound Clip in the Event Browser. Drop into a Timeline and edit away. Double click it to open the CC into it's own Timeline to make adjustments to it by itself.
Here is an article in the HUB about this very subject. And be sure to check out all of the FCP X and Motion mini-tutorials in the HUB. Free, we love free!