Help with heating core

Hello all im trying to do a stand up cuddly bear cake pan. After baking and cooling the cake tonite i went to remove the heating core and my bear bust into a million peices. I was pretty disappointed as i followed the directions exatly also i sprayed the pans and core with baking spray. I wanted to know if anyone had any tips on the heating core. What is the best way to remove with out busting the cake, and is the core even needed if i were to change the bake temp and time

thanks for all the help!