I cleaned & greased the CV joints and installed new boots when I recently replaced my old engine with a less old one. Rock Auto sells kits for as little as $4 each, I splurged and got the $10 kits. I have a parts washer to clean the grease that I couldn't just wipe off and then used Brake Cleaner to get the joints very clean. Then grease and install the boots. It's messy, so cleaning up after it's all done (with brake clean) finishes the process.
Instead of $300 for a pair of axles (as listed earlier in this thread) mine cost a total of less than $40. I sort of agree that the hardest part is getting them out--putting nice clean ones back in was a piece of cake. I made a tool--cut off a 6mm allen key and used rtv to glue it into a 6 mm deep wall 1/4 in. drive socket. A little breaker bar and a cheater bar helps break the axle to trans. bolts loose.
If that youngster AZLVR can do it, you can too. (I'm 66)