Always a good idea to pull the negative battery terminal - just make sure that you've taken the appropriate precautions if you have anti-theft (alarm, audio system, etc.) equipment in the car.
Also, highly recommend against using the Bosch sensors - go with OEM Denso O2 sensors. Spend a little more money, but have less headaches down the road. Bosch ones will still "fit", but many have experienced a sensor thresholding issue or impedance mismatch. In other words, the Bosch sensor does not output a signal within a range that the ECM finds acceptable. Most common complaint - re-occuring check engine light and/or poor fuel economy.
I verified this behavior myself, seeing as so many people have reported poor performance. Both two upstream sensors - Bosch Exact Fit and Denso OEM - btoh were plug and play. Bosch cost me $75, Denso cost me $135 - immediately had problems with the Bosch sensor, played about with it for several weeks before I gave up and replaced it with the Denso unit. The Denso sensor worked perfectly. Since the sensor will probably hold up for 90K+ miles (assuming it would act like the OEM Denso sensor), the difference in price is in the noise.