For ECU and harness pinouts, refer to the Honda Civic Service Manual. I've uploaded one, so this link should always be good to use:
https://docs.google.com/file/d/0B0Fn...it?usp=sharing
Running without EGR is fine. I've been doing it for almost 2 years now. It does seem to prevent the car from going into lean-burn (which is why I have it disconnected, long story). You'll still get good mileage though.
To order the EGR valve you can go to HondaPartsNow.com for OEM stuff or go to any local parts store and special order the parts store brand (~$220).