Use the mighty Pen tool to conquer complex outlines
Use the Pen to make the initial path. Get as close as possible, but there is no need for complete perfection. we will refine next with the Direction Selection tool.
After creating the path, rename it Work Path in the PAths palette. Use the Direct Selection tool to reposition any anchor points and also to adjust curvature.
Once the path is refined, press the Load Path as a Selection button at the bottom of the Paths palette, or hit Cmd/Ctrl+Enter. Applying a 1-2 pixel Feather will smooth things out (Select>Modify>Feather).
For smaller gaps at the top, zoom in, use Quick Selection to select them, then hit Delete. Now you can use a new background beneath, and play with various Adjustment layers to blend everything.