Those 2 codes combined (BOTH front and rear O2s) are usually caused by a cracked or split vacuum hose, often found at the vacuum T under the plastic throttle base cover on non-turbos. Don't be like many who replace O2s only to see the codes reappear, not realizing the real problem.....a vacuum leak.

Now, as for "special O2 sensor tools", a 7/8" or 22mm wrench works just fine.....always. No special tool required for 850s. Even if the sensor is VERY tight, being that you'ld be replacing it anyway, just cut the plug wires and used the closed box end.