PB Blaster is a product like Liquid Wrench, if you are familiar with that. It's considered superior to Liquid Wrench by most mechanics that I've read, though I'm personally more familiar with L.W. It's basically a type of penetrating oil that is formulated to loosen rusted or otherwise stuck bolts and other parts. You spray it on the joint, tap the joint to set up vibrations that help the oil to penetrate, then wait a few minutes. It really is one of those garage must-haves.

And don't worry about breaking your rotor apart and getting parts inside the distributor. Most likely if it breaks apart it will be in big plastic chunks that you can easily deal with, or in the worst case pick up with some needlenose pliers. Most likely it will break off in one or two pieces, though.