Let me make sure I understand, you want to copy part of an Eagle schematic (the .sch file) so that you can paste it into the library and use it as the symbol for your new part? The only useful part you might get from the schematic would go towards defining the symbol. The package would need to be defined seperately or copied for a board (.brd) file. A device needs both a symbol and a package to be defined.
) the part to my schematic and even used it to lay out the board.