on a socketed/chipped ecu the o2 can be disabled, but it would definately need to be tuned.

turn off the car, disconnect the ecu for 30 seconds then recheck the codes. i've never seen codes not repeat.

you can replace the vss. it should be sticking up from the tranny case (i think it's held down w/ 1 10mm bolt) w/a plug to it.