I would take a look at these people

http://www.screentekinc.com/

Using something with a Wacom digitizer is
a better solution than what a pressure
sensitive screen gives you which is in
essence only mouse emulation.
But the real issue is even if you get it
working there are really no programs to
make full use of the inking capability.

For what you are talking about I think you
would have a better chance of putting the
iBook guts into the PC case than getting
the hinge to fit in an iBook
You might want to think of a hinge and
slider mechanism such as this. Even if you
have to make a connector that allows you to
unplug adjust the screen and than plug the
connector back in.

One last note I have responded to this post
using nothing but a 3lb. slate PC
Traitor you might say! Yes but I am
a Professional and I need tools not
ideology to get my Job done.
Unfortunately Mr. Jobs does not want to
offer us these tools.
Joseph