It needs to be really far off to not work. Dont remove the window ring (reluctor). Leave it in. Take the cap off. Rotate the motor using a socket on the alternator nut (I dont recommend grabbing the IC fan to do it like gnttype suggests). Push on the fan belt and put tension on it if its not tight enough to rotate the motor. Rotate it clockwise until the window on the ring is almost aiming toward the drivers side fender. Slowly turn until you're at TDC. Make a mark on the cam sensor body to show where the window is aiming...something accurate. Remove the retainer bolt which holds the cam sensor in the block. It helps alot if you have the intake tube off before you start. Take your time and be patient and work slow during this cause it can be a pain to get your fingers on the bolt. Pull the whole assembly out. The shaft will rotate as you pull it out, just like a distributor. Keep an eye on where the window ended up rotating to when you got the sensor all the way out. You'll need to remember this location when you go to drop it back in. When you're ready to drop it back in, just start it where that window was when it came out. As you drop it in, the ring will rotate back to the position it was when you started. If you dont have it on the right tooth, the sensor shaft wont drop in properly and engage with the oil pump shaft slot. If its not dropping in all the way, you probably have it a tooth off. Dont force it. It should drop right in (with the exception of the little resistance you'll get from the O-rings). Screw in the retaining bolt but dont tighten it all the way...just finger tight. Assuming the window on the ring is where it was when you started, now take a look at the little rectangular locating notch for the window ring, which is 180 degrees around from the window. Rotate the outer body of the cam sensor until this locating notch lines up with the notch on the body of the cam sensor. Its a locating mark that was put there by the engineers to make engine assembly go quicker. Once the locating notch on the window ring is lined up with the notch on the body, tighten the retaining bolt, and you're ready to go. Theres not need whatsoever for any expensive calibrating tools or voltmeters. These marks were put there for this reason.
