This may be one of the best uses of the (late?) Action system that I've seen. It gives a very 3-dimensional feel to tactics and movement, and actions really do have consequences.
Action has taken some hits in the past for not emphasizing role play itself. The templates and the chapter on Individualizing Your Character takes care of much of that, but the player IS going to have to do their share of the work. It is all too easy to bring the hack attitude into the Wild West mythos. Here is where many of the tools for the gamesmaster come in. The system does reward the player for playing "in character," and does it pretty well. Shucks, ma'am, it's even fun to create characters in Gunslingers. Haven't had this much fun creating a character since Traveller!
Yep, there are some amusing spelling errors. I'm fairly sure that when Mark says "Each player should select a cultural decent from where his character’s forefathers originated," that he really meant "Each player should select a cultural descent from where" etc. (Even then, I'd have made him rewrite the line for clarity.) So yeah, it's not 100% perfect - nothing is.
But it's a good fit for a great western adventure. I think you'll enjoy it. It's worth at least twice this price, and you'll rarely get this much adventure for this price.