Regarding the "worth" of overclocking... personally I wouldn't bother. My rule of thumb is if a computer "feels" too slow you're going to have to roughly double the speed to really notice a change. (Granted your iBook probably isn't twice as fast as the iMac, if that's your benchmark for "fast enough", but if the problem is less cache on the iMac you're not going to be able to close the gap much no matter what you do.)

Personally, when it comes to soldering I've always found getting stuff off to be a *lot* harder than putting it on. :^b