"My iBook is not booting, full speed fan, black screen"に関する回答A bit late to answer, but your issue looks like the dry solder issue iBook G4 was plagued with. And yes it can be fixed: https://macintoshhowto.com/hardware/how-do-i-get-my-broken-g4-ibook-fixed.html
"Mac with most repairability (10 out of 10)?"に関する回答The Macintosh Portable is the easiest to open and access it's internal parts. On the desktop line, some modeles like the PowerMac 7500 is really easy to open too.