I don't know of anythng that will remove the stain and odor of motor oil soaked into wood. The guy really knew what he was doing. Hopefully he didn't also spill oil around outside to the extent an environmental cleanup is required. For the purposes of negotiating a price on this place, when estimating costs to repair, figure on replacing all contaminated materials, including subfloors. You must also consider the cost of disposal before you enter into this purchase. In most places, oil contaminated waste can't just go to the landfill. Be sure to call the local disposal company to find out what waste disposal is going to require / cost. Don't agree to purchase until you know all the potential costs.
When pulling carpets and padding, try to keep everything contained in as small area as possible. Don't allow contaminated materials to drip or be dragged across clean areas. Wrap it in plastic where it is removed. You won't be able to salvage soft finish materials like carpet and most exposed finished wood surfaces.
Use all the above to your advantage in negotiating price. Then, you may be able to clean wood and seal it. A citrus emulsion cleaner is your best hope. It is capable of dissolving oils and allowing you to extract the residue with a water extraction machine or shop vac. Its an outside chance this will work. Finish by scrubbing down with soda ash (baking soda) which will absorb the sulfur. Once it dries, you should be able to seal the wood with Kilz and then finish. The result should be odor free, but no guarentees.