Rubs and spices

You definately want to cooks ribs indirect, whether on a kettle or a gasser.
The set up you described in your kettle is indirect.
I don't marinate ribs when I do them, just rub 'em shortly before they go on the pit.
I like hickory with pork and will throw some chunks or splits on the coals to get the smoke flavor.

Start with a basic rub using ingredients you like. I started with salt,pepper, and garlic. I went from there. I listened to people I cooked for and used their ideas also. I think a basic rub could be salt, pepper, onion powder, garlic powder, Hungarian paprika, and cayenne. Notice I did not say onion salt or garlic salt. However, if that is what you have on hand, use it if you want too. I did this off the top of my head. So, feel free to use it change it whatever you would like. Hope this helps.

As the others have stated you are going to want to cook the ribs indirect on the kettle. I have cooked many a rib this way and it can be done fairly easily. Besides moving the coals to the side I like to put a water pan under the ribs. I also do not marinade my ribs just rub them down a wrap them in plastic wrap and let them rest in the fridge for a while.

As for rubs I like Dizzy pig dizzy dust on mine. http://www.dizzypigbbq.com/

Almost forgot wood I like apple and hickory mixed.

I make a marinade using Oranges, lemons, salt, pepper, paprika, mustard powder, crushed garlic. I use fresh oranges and crush in blender, and do the same with lemons. I also use bottled orange juice. I will also throw in a little teryaki sauce and some soy sauce. I let the ribs (St Louis style) marinade over night. The acid in the orange and lemon tenderize the meat. I then smoke on a kettle grill, indirect. I use hickory wood chips, soaked, and add them directly onto the fire as needed (when the smoke dies out). I will usually leave them on grill for about 4-5 hrs. At about 4 - 4-1/2 hrs, I brush on a mixture of Chris n Pitts BBQ sauce and usually KC BBQ sauce, let it continue to cook/smoke for another 30 minutes, brushing on another 2 times. I have been complimented quite a bit on my ribs. I can't wait to use firewood to smoke my ribs on a drum smoker instead of on my kettle grill.