Has anyone ever done this before?

You want to put an iBook G4 logic board in an iBook G3? Yeah... There are numerous reasons why that's not going to work, besides the board being physically different.

closest i think you can come to doing that is just to put on the bottom casing and the screen back from a g4. the frames are really different. trust me, i've had two of them apart at once and the innards look quite different.

I'll just get a g4 then.

-Zach

To make your iBook G3 into an iBook G4, you're going to need a fair number of parts. This is a question that was a bit more common back when the iBook G4 was still shipping. Anyways, here's a list of what you'll need:
- logic board
- lvds cable
- reed switch/inverter cable
- heat sink
-dc-in board
- fan
- frame
- optical drive - you *may* be able to get your slot loader to work
- optical drive ribbon cable
- hard drive ribbon cable
- top case - the connectors changed a bit - and this will have to be one that corresponds with the model of iBook g4 board you have - as some use adb, others usb
- airport extreme card (if you intend on using wireless)

You can probably expect to pay about $200-$300 for all these bits - I'd advise buying the lvds cable and reed switch/inverter cable new from your local apple reseller - as I don't trust used ones. If you're going to go the DIY route - buy a broken iBook G4 (12" with a cracked lcd - and reuse your panel and outer plastics) or one with a bad logic board and a good board.

If you elect to buy a good working iBook G4 - your display housing will move right over (assuming you get a 12"). The bottom case *may* work - but your slot loading drive will look a little weird (the screw holes did not change between the g3 and g4.