Front Axle Boots

i know alot of my friends with older civ's have this problem...the cracking and eventual decintagration(sp) of their axle boots.

i was getting my tires rotated and oil changed at my buddies garage when we noticed my axle boots are beginning to crack (not all the way through, just on the surface of the rubber).

i tried to solve the situation temporarily (strapped for cash) by covering the cracks with a silicon agent but i dont know how long this will last. does anyone know where and for how much i can get a set of new axle boots for my car, and is it hard to replace them?