When you enter the Den, make your way south to where you found Anna. Go to the room with a coffin (it's directly to the right). Talk to the man standing beside the coffin, and ask to see the mummy. Tell him that the mummy is a ghoul, and scream out Woody's name. He'll run away, and you'll get some experience. Now, it's time to get your car.
To get the car, go to Smitty's workshop, and tell him that you have the part to get the car working. He'll charge you $2000 to get the part installed. Say that you're going to get installed, and then barter the stuff that you found in Vault City for some money. Install the fuel injection system for $750.
With your car, get the Power Armor from Navarro. This time, it'll be a lot easier to get everything (especially with the automobile). You'll need the armor for Redding. Anyways, head to the Vault City - Gecko block now, this time with your Power Armor.