don't forget, if you are using the GOG version, you will need to update your game as described here first.then you can extract the FAM folder from this mod to the DataPermMods folder (so you will have DataPermMods\FAM\skyhw\clouds95.dds). if you won't get the location right, you will only have the solid yellow sky.
On an unrelated note, how do I replace the intro with the higher quality one found here?: http://www.ttlg.com/forums/showthread.php?t=112595Just curious.