There's really not too much that HAS to come off to get it changed. The plastic shroud that is behind the crank pulley will need to come off, and it will make your life a little easier if you remove the acc'y belt. The crank sensor actually connects up near the cam sensor, so that too will need to be disconnected.
Once you get that all off, you will have a somewhat difficult time getting to the sensor itself. The bigger the hands, the harder it will be to get to. You'll need to be under the car too. The sensor is held on by a couple small bolts, very much like the bolts that hold the DIS module on the '89 thru '93 SC's. I think they are the same size bolts. Getting it off, shouldn't be too bad, but you may need another couple hands from above to help you get the new one on. Just make sure that you get the spacing correct though. You'll need to rotate the crank so that the veins on the back side of the HB pass through the sensor. You'll see what I'm talking about when you get under there.
Also, just a note to think about. Crank sensors occasionally go out due to life, but most of the time, they fail because one of the veins hit it. This is due to the stock balancer starting to separate and fail. I'm not going to sit here and tell you that's what's wrong, but do keep an eye on it. If you install a new sensor, and it fails shortly down the road, that's one thing I would be looking VERY close at.