The pictures tell the story. Put the car up on a lift and remove the lower radiator splash shield by pulling the 10 -12 plastic push-pin rivets. Shop mechanics work around the oil filter adapter and front motor mount, but you might want to remove the filter adapter for room. Other posts on that job. The post 2000 Northstars have 2 different CKP's, pre-2000 are the same unit. The CKP and connectors only go in/on one way. The connectors are their own chore to disconnect.....takes dedication. You MAY need to go to a dealer for a "CKP relearn procedure" if you have driveability problems after replacing both - the CKP's essentially are the timing triggers for the entire ignition system, coordinated with the CMP (CaMshaft Position sensor) for cylinder position.
CKP's set 4 codes - P0335 & 6 and P0385 & 6, depending on which is setting the fault code. You MAY also see a code for "stall or near stall detected".
If you have no P0340/41 codes, don't fool with the CMP. It's in the front lower portion of the rear cam cover, sort of below and behind the P/S pump.
If you anticipate doing ANY electrical, electronic, engine, or transmission work on your car, you NEED a Helm/GM Factory Service Manual either from eBay or
www.helminc.com ($135) or subscribe your car for 3 years to
www.alldatadiy.com: manuals, TSB's, recalls, diagrams, all codes, all modules, labor times, everything and much more. (Forget Chilton's or Haynes: far too generic for any in-depth work.)