I have a decent Nikon film/slide scanner, but if I had thousands or even hundreds to do I wouldn't be doing them myself. For one thing, it takes a lot of time, work, and processing power. For another, the pros have better equipment and better software. As long as you use a good service, the results will almost certainly be better than what you could do on your own unless you want to spend a lot of time doing it.

It's fairly expensive, so you're going to want to go through the slides and pick out just the ones you want to scan. Get a good hand viewer for this. You can either get a light board and a magnifying glass/loupe, or a battery operated hand viewer. I have this one and it works reasonably well:

http://www.bhphotovideo.com/c/product/40322-REG/Pana_Vue_FPA001_6560_Slide_Viewer_1.html