Narcissus Build

So I've been working on a project for my school using the BeagleBoard-
xM and have been writing some drivers for custom hardware we've built.
So far this hasn't been too much trouble as we build our own kernel
and have the source tree and all that needed for building modules.
Recently, we've switched to Narcissus build for time reasons and now
we can't build modules because we don't have the source tree used for
the specific build, or a config file to use for that. I was wondering
if anyone had any advice as to how to get the correct kernel source
tree set up for a particular Narcissus build?

Also, we've considered just using our build of the kernel but can't
get Xfce running on the platform. Are there any good tutorials on
getting Xfce to run on a fresh Angstrom console-image build from
bitbake?

And finally, not sure if this is the place to ask this but, does
anyone know of a nice tablet oriented GUI or windowing system that's
lightweight enough to run on the BeagleBoard? Gnome 3 looks like good
option but after some reading seems like it will be too slow and heavy
duty for such a platform.

Thanks in advance!

Perhaps you can retrieve the kernel configuration from /proc/config.gz ?