If you've got the Warlords edition, you shouldn't need the patch because everything out of the box is as up to date as you're going to get it.

3rd party mods .... there are a staggering amount of top fan-designed maps floating around and there are some historical battles available for download - check out http://www.totalwar.org/maps/for more info.

As far as stuff like Total Conversions goes, I'm afraid Shogun isn't exactly mod friendly in that department ( understatement? ), so there aren't any around. Soz about that.