smokyMcSmokster, take a deep breath. You don't need to worry like you are about the creosote buildup, a natural part of burning wood and charcoal. That buildup is not only creosote but it also has fats and oils that have evaporated off the meat with internal liquids. The temps in the smoker kill anything that could live in it. All that buildup is natural and part of the seasoning process. It helps seal the WSM leaks. I have probably used my WSM 30-40 times since opening the box the week before Christmas and haven't cleaned the interior yet like you described, probably never will. I just clean the grates and the water pan with soap and water.
The only time you need to worry about the buildup is when you see it peeling, which can happen after a few initial smokes and later after a period of inactivity. The exact same thing happens in Weber Kettles. If you haven't smoked all winter for example, you may see big sheets of buildup hanging loosely. When that occurs just use a grill brush and gently scrape the loose pieces off over a trashcan. Please, no oven cleaner.
Since you have used oven cleaner you need to do another burnout of your WSM to ensure you don't have any chemicals left that could taint the meat. Use wood and charcoal, about a third of a load is plenty, no water, vents full open, and let the temps run up in excess of 350F.
In the future, don't avoid the buildup, embrace the buildup. It means UBSMOKIN!
On the Virtual Weber Bullet website there is a set of guidelines about taking care of your WSM. Oven cleaner is never mentioned.