I would recommend removing the motherboard from the system, then bring both the motherboard and CPU to your kitchen sink. There you should be able to wash the thermal grease off both the CPU and the motherboard (socket) using water, dishwashing liquid, and a toothbrush.
After the grease is completely cleaned off I would recommend a final rinse with isopropyl alcohol
to remove any potential residue from the cleaning process. Once the grease and any cleaning residue has been removed I would use compressed air or maybe a hair dryer to blow out any water and insure that all of the components are completely dry.
Once you are sure that it is clean and completely dry, you should be able to reinstall the motherboard and processor. If the pins aren't bent too far you should be able to straighten them with a tweezer, hemostat or needlenose pliers. If any break then a new CPU would most likely be required. Let me know how it goes. Scott.