Vauxhall Corsa - Engine Management light - O2 Sensor?

2004 Vauxhall Corsa SXI Twinport with 60k miles
1.2 Manual 2 Wheel Drive

Hi,
Engine management light has come on my vauxhall corsa dash, Done a diagnostic check and it shows the bellow fault:

P0141 O2 Sensor Heater Circuit High Voltage (Bank 1 Sensor 2) C-31

Does this mean the O2 sensor needs changing??
Is it the front or rear sensor?
Is it a DIY job that a beginner can do?

Many thanks

Akeel
July 2011