Well you could see if the ribbon cable for the trackpad has come loose. If you take the keyboard off (Same procedure as adding RAM), then you'll see the little cable for the trackpad. Its an orange flat cable with black lines going through it. You'll need to also take the AirPort Card out, and then take the 2 screws off which will enable you to take the plate off to get to the connector.
When you take the plate off, you'll see the extra RAM slot, which may or may not have RAM in it. To the right will be a wider flat cable which is the keyboard, and the next to that you'll see the much thinner cable which is the trackpad. See if it has come lose, or if its damaged. You may even want to reseat it. All you have to get it out is pull upward on the clip that holds the cable in place and the pull out the orange cable, then push it back in and then push the clip back down. Then put the iBook back together and start up your iBook and see if the trackpad works.
Before you do all of that, its a good thing to shut down the computer, unplug it and even take the battery out. You don't want any power going to the iBook while you do this just to be safe. This does NOT void the warranty as the section you're getting into is a user expandable section (RAM and AirPort Card). Also, make sure you ground yourself by touching something metal and don't rub your feet on the carpet while working. This sounds like a lot of work, but the whole process should take well under a half and hour. But take your time, there's no rush.
If you have any questions or problems, please feel free to respond.
