Notebook DualScreen installation for special purpose

[Master One]

The following situation:

- One IBM ThinkPad T42p (Gentoo Linux with KDE, UXGA 15" panel 1600x1200)
- Two IBM PortReplicatorII (has 1xVGA & 1xDVI)
- Two LCD screens, each connected to one of the PortReplicators (on VGA port, 17" with 1280x1024)

This is what I want:

When using the notebook without the PortReplicator, it simply should work as usual with a single screen (= the notebook's panel).

When the notebook is connected to the PortReplicator, it should use the notebook's panel and the external LCD screen (the external screen should mainly be used to have a Konquerer window open to view a network-camera-setup).

Is there any possibilty, to set up this environment, so that it automatically detects, if the external screen is present or not?

If the general setup should work out fine, I am still unsure, how the second screen should be operated (using cinerama may not be the best idea, starting another xserver session on the second screen may be the way to go, but how would it be possible to use the notebook's keyboard/touchpad/mouse independently on both sessions?).

I am still new to use Linux on a desktop, and I do not own the above hardware setup until now (I am still considering on purchasing that notebook), so I would be very grateful, if someone has any idea concerning this intention.