It didn't take a great deal of time to learn the nuts and bolts of it; it was mainly a matter of getting all the software together and then working my way through utahjazz' tutorial. My first units took a long time to make. Reaching the stage where I could remember all the stuff, and just sit down and make a unit from start to finish without needing to look things up and properly understanding what I was doing, took longer. And reaching the stage where my units were pretty good took longer still, as you can tell if you go through my units list sequentially. The fact is that the many flaws of Poser and the eccentricities of the Civ III flic format make unit-making a complex and often tedious business, quite apart from the artistic problems involved. It's this, rather than the artistic work involved, which is why I'm amazed at how many units Sandris makes; the thought of putting all those storyboards together, checking all those palettes, and (worst of all) making all those units_32.pcx chills me to the bone.
That said, simple units, especially those where you can use pre-existing animations (such as those uploaded elsewhere on this site), are not at all difficult to make provided you're diligent and follow the tutorials carefully. Anyone with Poser can knock out some simple swordsmen, spearmen, workers and so on using the templates that are available, and this is a good way to learn the unit-making process. The tricky stuff comes when you try to get more imaginative and put wraiths wielding flaming swords onto the backs of monstrous winged beasts.