Back at it again with the newbie questions!

The guy I got my ball python from said that at her size she should be eating pinkie rats or hopper mice. All I was able to find at my local pet store, though, were pinkie mice, and I got a little box of 6.
My question is, since pinkie mice are obviously small, should I feed more than one to make up for that? (Is there something wrong with doing so?)

I still have one other store to check, so hopefully I won't be stuck with pinkie mice forever.

Also, I understand that moving to a new cage is bad, but should I remove hides and such for feeding? My Biology teacher does this, but those are all for live feedings, so for pinkie mice I wasn't sure.

And last question, should I like... heat the mouse up? I mean, logically I assume a frozen mouse =/= good for cold blooded snek. Should I drop the baggy in warm water, do I pull it out to 'thaw', do I... do I microwave it?

Thanks in advance for the help!