My son got a spectrum 4-4-0 model for Christmas. I needed to switch out the coupler and to do so I took off the wheel truck. When I went to reassemble it the screw wouldn't hold and it appears there is a piece up inside the body of the tender that the screw needs to hold to. However I can't see how I can take the tender apart to do this. Any ideas or instructions regarding taking the cover off this tender would be greatly appreciated. It's the Baldwin modern undecorated, model no. 80101.