I thought you had already done a tuneup or had one done, you just may be onto something. Follow the advise given here, it is all good. I usually just twist till I get some movement at the bottom, you will know when it happens, then pull the wire off. As a last resort you can always break the porcelain part of the spark plug off, reach in with some long neck needle nose pliers to remove the broken piece which will have the rubber still attached, blow the hole out with compressed air and then remove the rest of the plug.
The antisieze doesn't always prevent siezed spark plugs, but it does help and as Chris mentioned check for proper torque. His method is a good rule of thumb for gasketed spark plugs, which I am sure you have. It is easy to over torque them and under torquing can be just as bad. The spark plugs loosen off, then compression blows them out of the hole usually taking some of the cylinder head threads with it.
