If you want to "test the waters" and want your figures 28mm and painted you could do worse than pick up some pre-painted figures from Doug @ em-4 (em4miniatures.com).
They're available in packs of 5
Set #1 - Sheriff; Gambler; Gunslinger; Mexican and an Indian.
Set #2 - Buffalo Soldier; Mountain Man; Soiled Dove; Farmer and a another Sheriff
and Set #2 comes with rules and a town plan on a CD.
If you don't like the rules you at least have a variety of figure types to be able to try out other "downloadable" rulesets.
The other alternative for pre-paints would be to check-out the Bazaar here on LAF as I know that v_lazy_dragon has a few painted "cowboys" which may fit your needs.
