Where is the crankshaft sensor on a 1994 Oldsmobile 88

On the passenger side behind the crankshaft pulley. You have to remove the serpentine belt and crankshaft pulley, which is best done through the wheel well. Removing the pulley can be quite difficult as some of these require a special puller. It may be worth the 1 hour of labor to just have a shop do it as this could consume a whole day if you don't have the tools for the job. With the crankshaft pulley off it would be wise to inspect/replace the crankshaft seal. There is also a bit of a trick installing the new sensor, it has to be aligned carefully so that the crankshaft pulley vanes hit it.