Even though you do not have AppleCare, the apple store can replace specific keys on most computers. I would make a genius bar Appt at your nearest store just to see how much it would run you so you can get it installed correctly and the new keys will be under warranty for 90 Days.
Idk how true that is. I went to have 3 keys replaced, only for them to tell me they would only replace the entire assembly.
OP be careful about what keys you buy. I ended up replacing mine, and it can be a bit tricky, if the Apple store will do it then you should definitely go there. Otherwise I bought my keys from http://www.replacementlaptopkeys.com
If you've worked on laptops before, you shouldn't really have a problem replacing the key. Just go to Youtube and follow the instructions.
Actually, I think you have the same laptop as me, so if you go to that site, select the AC06 as the key model, to ensure you get a backlit key.
To replace, basically you are going to take a small flathead screwdriver, get under the key, and pop the plastic grips holding the key to the assembly off, then you grab the new key, and just press and pop it in. It's pretty simple and easy for keys like the one you want to replace. It's really worth it to do it yourself in this case.
I had to replace my delete, enter, and a regular key. Not so fun.
Hope that helps.