"How to put a key back on?"에 답변The white scissor hinge will need to be carefully removed from the key and replaced back into the keyboard, and after that the key cap can be replaced. Taking time to study how it all fits together and being gentle with the parts will prevent damage to the clips.
"Are all A1278 logicboards swapable?"에 답변A1278 covers a range of models, even including the 2008 aluminium MacBook, and not all parts are compatible. A 2009 MacBook Pro 13 inch needs a Core 2 Duo board from 2009 or 2010, but unfortunately the later i5 board is not a compatible replacement.