We make our own KC rub. A good starter recipe would be here:
http://bbq.about.com/od/rubrecipes/r/bl91211a.htm
I tend to use a little less cayenne than they call for and a little more sugar to make it tollerable for the kiddies.
Not sure on the gas smoker as I've used electric and wood. I would think the gas is a bit like the electric in that it's easier to maintain a consistent temp which is key. You don't want the temp spiking.
I think I remember reading that apple wood is a bit too light on flavor for ribs, but haven't tried it. Worked great on chicken. Gave a bit of a sweet smoke.
I'm sure some others will chime in soon.