I would think you'd be happier with a separate machine to run Windows stuff. Emulators need lots of CPU and RAM to run effectively - something that's difficult to have in a PowerBook.
Yes, you can run emulators on a PB. How well you can tolerate it probably depends on your pain threshold though.
If you insist, max out the RAM and get the fastest PB CPU.
The network (GB Ethernet) and USB2 stuff is built-in so that shouldn't be a concern (though you will need a USB hub if you plug in more than 2, IIRC). I think the monitor stuff was addressed earlier.
HTH.
Cheers,
Scott.