Driftwood that I found laying around has been the best addition to my tank to date
Id like to see some pics.
As for prepping it, I would boil it for 10 minutes or so and then let it soak in water for a week. It will probably still float but this will help out.
If it's too big for a pot then put it in a bucket, anchor it down with something, and pour boiling water over it. Bring more water to boiling and keep pouring it over the wood until it is covered and then just let it sit in the hot water until it cools down. The water should be more than hot enough to kill anything on it.