Resposta para "No serial number under About This Mac post swapping the CPU."I'd say take it into a Apple Authorized Service Provider and have them run AST on it. It should, if the serial number hasn't been set, prompt them to serialize the unit. Otherwise, you're likely looking at having to get your hands on the serializer tool. You'd want to locate Blank Board Serializer v 1.1.1 .
Resposta para "Display Backlight not working after replacement."This shows the location of the backlight fuse. Check it with a multimeter. Should measure 0 to 1 ohm. If it doesn't, you're looking at a logic board replacement and/or component level repair.
Resposta para "The machine powers but nothing else happens"Likely that either the display has died, or the video card. I would suggest hooking the machine up to an external monitor to see if you get video. If you do, likely it's the display. If you don't, then that would point to the video card. I've been replacing more and more of the displays as of late for customers, so my gut says it's probably that.