Place the sky_camera at the world origin. That's 0,0,0 coordinates. You can find it easily by looking at your 2D views, there's a blue line running down and one running left->right in each view (top, right, front, etc). Make sure the sky_camera is right at the intersection of those blue lines in each 2D viewport. Next, if you have fog settings in your map via an env_fog, copy the values from that entity to the sky_camera so that the skybox fog matches up with your map's playable space fog. Leave the skybox scale at 16x, almost all skybox models are 16x smaller than the original models. Then, build your 3D skybox around your map in full scale. When you're done with that, select all the stuff you want to be 3D skybox AND the sky_camera, move it to somewhere outside your map, then use the transform tool with ctrl+m to make everything 1/16th size. You'll see an X, Y and Z with the number 1 behind it in a text box, if you want to scale everything down by 16 times you put 0.0165 in every box behind the x, y, z and hit enter. All that's left now is to seal the skybox up with a box around it and boom, done. Make sure to func_detail everything except displacements in your skybox though, this saves VVIS from having to calculate visibility data in a part of the map that won't be visited by players at all.
heh, I got ninja'd by 2 people. but the point still stands. Also, don't be so impatient. Not everybody is online and ready to answer everybody at any time, more often than not you'll have to wait quite a while for an answer simply due to not many people being online at a given time.