I am looking to replace the keyboard only or the TOP cover of the a1278. MBP mid 2012.
Discussing with a Genius bar tech guy, he recommended to buy the Top cover including the keyboard and backlight, apparently.
I found the top cover for 39 CAD+ transport. While the Keyboard only can be bought at +/- 10 CAD + transport.
Hope this helps.
PS: I think I will go for the TOP Cover, less risk with keyboard and backlight, power button too.