MCE will do a good job for you. Their prices seem to be about $100 above the price of the drive alone. And they keep the old drive, so it really costs more than $100, because if you do it yourself you can sell the old drive on ebay.
So if you do the replacement yourself, you can probably do it for a net of about $50. If you pay someone, it'll probably cost over $200. Of course, if you don't want to do it yourself, then it's $200 well spent.
I can only say I've done 4 iBook drive upgrades. They are not easy, provided you follow the instructions. But they are not easy either. The hardest part if getting the iBook case opened up. Once that is done, the replacement is a piece of cake.
Chris