I turned my WSM into a fireball once using wood. My water pan got all full of grease, and I had the brilliant idea that I would just burn it out. Lid off, door off, nice hot mesquite fire on the charcoal grate. Yeah, turns out that grease doesn't have to be in contact with flames to have a grease fire, you just have to get it hot enough. A WSM is just leaky enough that even when you shut all the vents, the grease fire will continue to burn and spurt flames out every available crack. The WSM ended up ok, but it burned hot enough to seriously soften the aluminum vents. One got a bent tab from me kicking it shut, and the top vent had all the stops bend out of the way so it can spin freely now instead of opening and closing. Thank goodness I have a stainless steel door, or I might have totally melted that too.
Now then if you are not an idiot like me and you're just cooking with wood, I think the big problem you're going to have is your fire will burn incredibly dirty. Wood fires need lots of air to make clean smoke instead of coating your food with creosote. The WSM is designed to choke a fire until it smolders. Ok for charcoal, bad for wood. That's why if you use too many wood chunks your food tastes bitter. If you were going to make a wood fire, it would need to be tiny, like thumb-sized sticks or something, and you'd be constantly tending it.
If you really want that wood fire taste on your meat, you'd be much better served getting a stick burner. Believe me, I've tried cooking on my WSM every way I could think of, and I've come to the conclusion that it is what it is--basically a charcoal-fired oven with a big water pan.
