You have the right idea. Any urine has a high concentration of acid and sodium bicarb (baking soda) is a neutralizer for acid. 69hemibeep has the right idea by soaking the areas with a concentration of water and baking soda. Rent a carpet shampooer with the chair attachment and go over the areas several times. If you should remove the carpet, I would just buy new and replace, but I would still use the above baking soda and water mix on the floors before installing. Sodium Bicarb can be bought at pool supplies stores in bulk at a good price. Note: Rats or mice are good at doing in your car also. Set traps around the area is best. Sorry to hear of your dilemma and the best of luck.