How hard is it to change the door glass? My door glass on both doors are scratched from years of being rolled up and down, Ive replaced all my weather stripping, I have 2 damaged doors that have perfect glass in them, Ive never changed these before and it's too cold for me to be out right now trying to figure out how, just looking for some info to read over to help me be ready when it warms up outside. Thanks in advance!