I had to pull the PS pulley when I replaced my water pump, but I didn't have any real problems. Make sure you have a PS pulley puller, not just a generic pulley puller. The instructions that came with mine were fairly clear on how to assemble the parts, and it worked on the first try. My kit had a ball bearing in it, which made life a LOT easier.
Just make sure everything is lined up properly, and the tool doesn't start leaning to one side when you're cranking on it. It will take some effort to work the tool.