I want to use my Raspberry Pi to give new live to an old PowerBook (Power PC) that seems to have a broken motherboard.
I would like to be able to use the wifi, conectors, keyboard and screen.
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What you're proposing is impossible.
First of all, PowerBooks (all mainstream laptops, really) use vastly different interfaces than the Raspberry Pi for things like the WiFi, the keyboard, and the screen. See this question, which talks about interfacing an old laptop keyboard to the RasPi.
For this same reason, you'd likely be unable to use most of the connectors. The Pi has pretty limited I/O compared to the Powerbook; you wouldn't be able to use the FireWire, VGA out, etc.
Finally, even assuming you could somehow interface the Pi to the surviving PowerBook internals, your new creation would not be nearly as fast as the original PowerBook. I talk about the Pi's performance limitations in my answer to this question, but to summarize: the Pi has a very weak CPU without a graphics-accelerated X server, which makes it pretty much unusable for mainstream computing.
You'd be better off buying a used/refurb laptop from elsewhere, rather than trying to cram a Pi in a place it simply doesn't belong.