You're not missing much, if anything at all. Every lens I've ever taken apart has been relatively simple. If it wasn't, it was because the lens itself was being difficult (ie. parts refusing to be unthreaded). I think a lot of it has to do with a cash grab -make it seem so overly complicated and daunting that you must seek professional help. It's the same thing with cars. Go to a mechanic and tell them you've never done an oil change before and they'll try to talk you out of it, say you need all these tools and all the things you could do to ruin your car, etc etc. and that you need to pay them to do it.
Originally Posted by clayne
Some people also just hear rhetoric like "NEVER TAKE APART A LEICA LENS!! THE PRECISION IS SO PRECISE AND THE SECOND IT COMES APART YOU'VE KNOCKED IT OUT OF WHACK!!!" and then just repeat it all over forums without having a clue what they're talking about. Well, I've taken apart nearly every lens I've ever owned and even some with built in shutters that weren't working and fixed them without a manual or anything. I've taken apart all my Leica lenses (28mm, 35mm, 50mm), some canon rangefinder ones for cleaning, etc. and they still take sharp and beautiful photographs. I even made to repairs to my Leica M6 without any instruction. It's mostly logical mechanics and yes, there are SOME things you shouldn't try...ever...unless you're trained and know what you're doing. But for the most part, you can dink around with a couple cheap cameras and learn the basics with just some precision screwdrivers, spanner wrench and some other simple tools most people have lying around the house.