There are 2 cables that meet at the shift plate. The lower cable is the one that's normally changed, if any. It runs between the shift plate on the starboard exh manifold and the transom.
Once the cable is disconnected at the top and bottom slide it in and out through it's range. It has to be perfectly smooth and slide nicely. Any restrictions or kinks will cause you fits well beyond what it costs.
You basically put the shift in forward,remove the drive, cut the shift cable bellows and remove the lower shift cable. Then remove the sensors on the pivot ends of the bell housing, remove the pivot bolts on either side of the bellhousing, cut the 2 drive and exhaust bellows. Now it's apart. Get your cell phone or camera and note the position and direction of all the clamps. It only goes together well one way.
Buy good parts, you don't need to save $10 and have it cause a poor seal or short bellows life.
When you put it back together you need the right bellows cement and you'll need a long thin straight blade driver for the bellows clamp that's straight in from the little round hole on the outer side of the transom plate. I also get good use from my 1/4" drive flexible spring extension, to run in some of the clamps.
To adjust the cable there are steps that need to be done in sequence. Best way is to watch achris's video.
