> I remember a while back that there was some discussion of
> using heat to break the grip between rusted parts.

I do a lot of this because I work on my own vehicles.  Up
here in New England, that means loosening parts that have
experienced lots of salt and winter for ten or more years.
The best stuff I've found for loosening rusted items is
Kroil.  Everybody that I know who has tried it loves the
stuff.  You can order it straight from the manufacturer at
http://www.kanolabs.com/.

Basically you squirt it and let it sit for several hours.
Perhaps do this two or three times.  If that doesn't work,
I usually try some heat from a torch.  The size of the torch
depends on the size of the parts you are freeing and whether
you are worried about discoloring the finish.  For a small
part like this, try a little propane torch.  Don't heat it
up red hot.  That's not necessary.

Good luck,
--Dave Shepard