Not too tough of a job. Just put an atx powersupply on my A4000. The tricky part is the way the atx power supply gets powered up. If you look at the power supply leads, there is a green wire. That one has to be set to ground in order for the atx power supply to actually turn on. You can put it to an on/off switch to turn you 3000 on and off, or just solder them together and use the powersupply switch.
As to the other pin outs, just look at the ATX wiring diagram and match them up with the pinouts from the A3000 plug. I used and voltmeter to check my voltages on both sides.
Pin outs here.
http://www.l8r.net/technical/t-amigapowerpins.shtmlor here:
http://www.hardwarebook.net/connector/power/amiga3000power.htmlAnd last, here is some info on the "tick" signal of the A3000 power supply and how to get around the problem.
http://www.liukuma.net/amiga/A3000atx/buildingdescription.htmlThis is what I did, but it's an "at your own risk" operation.
