Considering the fact that the power supply is missing, you can probably make a low offer.
try to open the screen a couple of times and have a look at hinges, if the gap between those and the casings are even, it's OK, if not... they are starting to go.
Those who are gone to a previous repair (Apple) have a serial number finishing by AA (or AAA, don't remember)
probably all of them will have a faulty power connector (repaired mine several times, never get something fine...just acceptable) but logic board is very easy to remove from the casing (just three screws and you are done)
Ethernet is not standard (nor any Cd-rom drive) but once again you can probably find a Wavelan wifi card.