To get it loose, pop it in a 200 degree oven for a few minutes and gently try it until it breaks loose. A little WD-40 or Marvel won't hurt. Now, take it apart and soak in the 50/50 antifreeze mix in the cheapest crock pot you can find. $5 at Goodwill? Take it out and rinse with plenty of clean water, dry it in a warm oven, oil lightly and reassemble. BTW, ATF makes a good pickling oil. Label the crock pot and for goodness' sake don't ever cook in it!
Kelvin