Actually, the PO171 code should clear itself after a couple of drive cycles. So if you're worried about pulling cables or wondering which fuse to pull, all you have to do is drive the thing (I think 2 driving cycles clears the code, IF t's gone).
Look for air intake leaks (as stated above), and clean the MAF really well. The O2 sensor is expensive, and many times isn't the problem; all it's doing is reporting that there is a discrepancy between what the engine THINKS it is burning, and what's ACTUALLY getting down the exhaust pipe.

'99 Tacoma Xtra cab V6 TRD
TRD Supercharged, URD 7th injector and 2.2" pulley, 32X11.5 BFG All-Terrains, OME 881 3-inch lift/Toytec AAL, 5100 Series Bilsteins all around, and ProComp 130 lights.
No I'm not some creepy naked guy...