1986 Toyota Pickup cleaning out squirrel cage

Heater problem
1986 Toyota Pickup 4 cyl Four Wheel Drive Manual 201K miles

This is the second time this winter that the mice have created a nest in the squirrel cage of my truck's heater fan. I paid over $100 to have it cleaned out in December; now I need to learn to take it apart myself. Is it just a matter of taking the glove box off, then taking apart the area where the blower motor is? And to prevent this from happening again, can't I put 1/8th-inch hardware cloth over the fresh air duct for the heater? Please advise! (And thanks!)