Yes you can!
The 13" MacBook (aluminum unibody) (Late 2008) keyboard can be swapped out for a newer on from a 13" MacBook Pro (mid 2009) The 2.0Ghz late 2008 model does not have the backlit keyboard but it does have the port for it on the logic board, so when you swap it out you may get backlit functionality on your late 2008 MacBook aluminum unibody!
There is no guide for doing this on ifixit that I could find, but it can be done with a little patience and a few tools... The hardest part is stripping the MacBook down and getting at the underside of the keyboard, which requires removing the logic board, the optical drive, and a couple metal crossmembers, most of which can be accomplished by reading the logicboard replacement instructions in the repair section of iFixit...
Hope this helps!