I wouldnt disable the o2 sensor unless you are looking to tune and make adjustments. The o2 feedback is very usefull so turning it off does you no good.
Most widebands out there: AEM, PLX, Innovate, can work as a wideband or a narrowband, your DME accepts a narrowband signal.
You can use only one bung in your exhaust and make it work however, if you use the AEM wideband to feed a narrowband signal and leave your o2 sensor unplugged you will still get a check engine light as it will be looking to see the resistance from the heating circuit. In this case you can leave your o2 sensor plugged in and simply not install it in the exhaust, or use a resistor.
- Marcin