Kdolloff,
Sorry, forgot to mention to use a strap wrench, it didn't work for me but it is the tool that, if I remember correctly, the knoxx instructions recommended using- so try that first in combination with heating the receiver.
Another subject, when you do get the kit and install it, be sure to follow the reassembly instructions carefully. There is a part in the receiver that you DO NOT reinstall. Folks experienced in reassembling their shotguns tend to miss this step and reinstall all the parts.