I have on that is split also. Looks like one half-shaft slides into the other one, so I don't think it is as critical as say a CV joint. However, trash and grit could do some bad things eventually. According to the Haynes manual for an 83 non-turbo, you can remove the snap rings from the U-Joint and remove the axel shaft. There is another clip ring under the boot that will allow you to get the half shafts apart and replace the boot. Might want to check those U-joints while you have it apart.
If you can find a good deal on a good used one it will be a lot less hassle than replacing the boot. The half shafts do come apart but they can be a bitch to do.
Rusty snap rings, lots of bearings and lots of spacers that will fall out and try to escape!