I'm not sure how to be able to use the SC1 units in my maps.. They dont show up on the units available to be placed.. And is it possible to make sure a certain type of dark templar appears? Like the one w ith the blade not the scythe everytime?

Yes, I too am curious how you get access to all of the campaign units in the editor, as well as the special campaign assets like the biodomes, huts, civilian cars etc.

In the "new map" dialog, modify the dependencies to include the other two mods for the Liberty campaign (I think).
Though, I'm pretty sure you can get away with only the storymode stuff. Maybe. :s

Well it was the dependencies! thanks! (File->Dependencies->add standard->select all)