Pontiac Repair: 99 pontiac grand prix v8, rubber elbow, water floods

Question
I have two questions,

my check engine light is on, and the code reads as a bad o2 sensor.  I am an extreme novice in auto repair, how difficult is this repair job, should i try to repair myself or take it to a mechanic?

Also, everytime i make a left hand turn, water floods my passenger side floor.  I recently replace the blower motorm and have double checked that the hose on the side is properly attached, and it is.  There is also a screetching sound when the water starts flowing.

Answer
Hey Dale:

whicho2 sensor is bad #1 or #2 the #1 is in the exhaust manifold on the side of the engine near the fire wall and #2 is under the car in the exhaust pipe. It just has a plug on it you disconnect and then unthread it from the pipe/manifold. The water problem is a plugged drain for the heater box. the drain runs through the fire wall on the passenger side of the car there is a little rubber elbow on the drain it plugges up with leaves and debris pull off the elbow and stick a pipe cleaner in the hole and it should unplug the drain. Also look inside the elbow sometimes stuff gets stuck in that as well.