Sorry for not chiming in yesterday. Before taking the soldering iron to anything, it's good to always check the power supply rails for proper voltages and remove the optional RAM modules (as I see you have done). What sort of tools do you have available? (oscilloscope, multimeter, temp-controlled soldering station) Given the age and relatively cheap construction of these machines, it's very easy to do more damage when trying to repair them.
-Josh >
