Subarulegacy96

On my 96 legacy, the air conditioning belt broke because of what I perceive to be a pulley that is freezing up. There are two pulleys for the air conditioner. The lower pulley was plastic and disintegrated. Any suggestions on how to fix the upper pulley and keep it from seizing up again. If this is simple I'm sorry. I am a newbie to the subaru world and mechanics world. But I'm poor so I'm trying to do some of this on my own. Any info would be great. Thanks.