First thing to do is remove the seats and the lid, back and sidewall of the Doghouse. You can remove the entire Doghouse if you like but we found it easier to leave 2 sides up.
NOTE: The nuts that hold your doghouse together are specialized clip on sheet metal nuts and may be rusted out. They may drop out or break while you're working. Save them where you can but you may need to run to a big auto parts or hardware store where they sell replacements for these. Bring an example with you as there are many different types that look very similar. They can be replaced by regular nuts but they will be difficult to reattach. The sheet metal nuts are design to catch the metal or clip over the edge and not need a wrench on both sides of the bolt to prevent it from spinning free.
If you have carpet and you can remove it you probably should. Otherwise cover it up with cardboard or plastic.