Warn is the best, and the next best is MileMarker.
To my knoweldge, they are almost the same thing though.
If it's worth doing or not, I think, depends on how you use the truck. If you only use the 4wd for things like snowy days, or dirt roads, then I'd say keep the stock auto hubs, they are just fine for that purpose. But, if you do any type of trails, then you want the manuals. When you change directions (forward to reverse) the hubs go from being locked forwards, then they unlock, and lock again in reverse. And vise versa if you go from reverse to forward. This action tends to grenade the auto hubs very quickly.
But, if you only use 4wd for things like snowy roads, and dirt roads, you don't really have to worry about that.
If you are remotely mechanicly inclined, you can do the swap. Just look at the directions that are in the tech library and they will walk you through the install. If you have ever taken off your brake rotors in the front, you have already done most of the steps involved. The only differance is you put it back together with slightly different parts.