Yup, the freezer trick is what I always use and it works great. The AS gets brittle with sub-freezing temps and simply pops off. Some people say to use heat, but I figure thermal epoxies are meant to cope with heat, so am not sure how well that would work. I would think the epoxy would get gummy if anything, but who knows.
To contact S&T:
http://www.sky-technology.net/home.htm and click on the contact tab...
Also, FWIW, I don't think S&T has an issue with thermal epoxy on the
outside of the case, but someone here (Aragon IIRC) did the "internal mod" and they gave him some flak about it. I imagine it does make it harder for them to replace components. They did honor the warranty though. Still, you might want to remove any external heatsinks because you may not get the original back...