Awh that's just sad. Is there no other place you can get your stuff from? That place sounds like the place that I had gotten my feeders from before I found out that Pet Supermarket sells sizes of feeder rats. They actually had a red tailed boa in the same enclosure as a ball python... no heat, only one half log hide that was barely big enough for the one snake. All of his animals look sickly, or just plain unhappy. I know what you mean about wanting to take it home, but not wanting to risk the possible outbreak at your own home.
It's not going to kill your snake. Just spray only the body (NOT face or head) and then rub it all over your snake's body. Spray a little in your hand, and rub it lightly under and on top of it's head.