New blower - lots of mice

[lcsdoug]

My blower fan had been making noise for some time and finally stopped completely. So I ordered a FourSeasons replacement #75810 from carparts. Then I spent several hours trying to figure out how to get the glove box out. The tricky part was the 3 trim pieces to the right of the glove box. After that was out and I removed the lower cover, I could see shredded material falling out. As I slid the old blower down I could see the entire housing and fan wheel was packed solid with mice nesting material. I don't know how it ever turned. Must have been half a bushel. Also the evaporator box the the left was packed. I couldn't get that cover off so I used the vac and a thin nylon body tool to dislodge the material. What a mess. When I got it back together everything worked beautifully. A happy ending.
I live in the country and the boxster is in the second garage away from the house.

My question: How do I keep the mice out of my boxster?