I'm looking for some advice on my 94 Golf.

I took it into Ray Fladeboe VW Dealership, in Irvine Ca, due to the
'check engine' light coming ON.  They say the O2 sensor is causing the
problem & say for $299, they can install a new O2 sensor.  This would be
the third O2 for the Golf.  The original O2 sensor was replaced with a
2nd O2 sensor under warranty at 47K.  The car now has 70K.

My questions:

1)  Is the 02 sensor replacement something I could do on my own?  Thus
saving me the obvious labor cost of having them do it.

2)  Are there any advantages of having them install a new 02 sensor.

Any help would be greatly appreciated.  Please email me directly.
Thanks.

Durby Suniga
RSM, Ca