The 1st gen x3100 graphics card can only support a digital resolution of 1920X1200.
So to answer your question no it will not run the 30" in it's native 2560x1600 resolution. If you run the 30" in 1920x1200 it will just stretch thing and it just doesn't look good. Hit up the local apple store and put their 30" display in 1920x1200 and judge for yourself.
I would suggest sticking with a 24"
The 2nd gen can push a 30" to its native resolution.