I have scanned a number of my slides with an entry level Minolta 35mm scanner and a couple of points are worth considering.
IMO a scanner that has the ability to remove dust specs is essential. I believe Nikon call theirs ICE technology. If you do not have that you will have to spend an inordinate amount of time in your image editor fixing this and the results will still be evident.
Another point, if you go for a second hand model be aware that some of them have a problem with slides on Kodachrome film. There is something in the dyes that reacts badly.
There is also the risk that some of the older scanners are not supported with drivers for the latest versions of Windows. I believe that some of the older Nikons are in this situation.
Try a search in DPReview, this subject comes up all the time.
If there is one constant refrain it is that it is time consuming however it does give you back up if you have some valuable images.
I lost almost eight years of slides that covered my Air Force time in a house fire so that may justify your efforts.