Our rescue is also in PA and we know some local homes that would be glad to take in corns if you'd like to avoid shipping.
However, if you'd rather send them to your friend out of the area, there are some basics to start with. Use a 30 or 40 hour heat pack in the box, and make sure to use an insulated box (if you're anywhere close to Lancaster County PA our rescue could provide you with this stuff), or we could even mail you the empty box and unopened heat pack if you're nowhere close to Lancaster.
As far as how cold is too cold, and how hot is too hot, that's a topic open for some debate, and depends on the reptile. But if you're above 50 in an insulated heated box with overnight shipping, almost everyone will agree you'll be plenty safe with corns. Our rescue prefers local pickups, but we do utilize responsible shipping methods regularly so please contact us if you have any questions, or if we can help provide you with the right box/heat pack.
-----
Jesse Rothacker
Forgotten Friend Reptile Sanctuary
www.forgottenfriend.org