The splined hub does not have to replaced with the half shaft. The hub can be pressed out. If you opt just to replace the hub, you will also need a new welch plug to seal the hub.
Before you start this, some of the manuals, and catalogs of suppliers, will describe what worn splines look like.
I suggest that you jack up the rear of the car, put it up on jack stands and apply the parking brake, and try to move the wheel. There should be no play at all. While it is up, it will be easy to check the u joints also. It may help to have a friend assist you and start the car, put it in gear and listen.
If you opt to replace the hub, check the half shaft also for signs of twisting. These cars have a habit of snapping half shafts. If you see a twist, usually at the differential end, replace the shaft. It is very easy at this point and will save a lot of trouble later. I recommend that you check both sides.
Also, do not switch half shafts from side to side.
The reverse rotation will put excess stress and cause the shaft to break easier.
A side hint. The hubs must be greased regularly to prevent the wheels from seizing. I use the silver colored anti-seize instead of grease. The color matched the wheels almost perfectly. The wheels require much less cleaning to keep looking good.