My background: I used to design and write software for film scanners. I also have a large library of slides and have digitized many.
There is a huge variation in prices and quality for slide digitization. As Bill said you can get cheap slides scanners that will do a reasonable job. For more demanding work there are "professional" solutions that cost $1K and up.
There are two key attributes to be aware of:
Resolution: The $100 scanners can realistically capture about 1200 dpi, or the equivalent of ~2 Mpix from a 35 mm slide. The really good ones can do an honest-to-goodness 4000 dpi (~20 Mpix).
Dynamic range: Slides are very contrasty and render dark scene tones with very high densities (up to D=3.6+ for a really contrasty film like Fuji Velvia 50). D=3.6 means a 4000:1 range of intensity from the lightest tone to the darkest, so the scanner must have very low dark noise to capture detail in such dark tones.
Only you can judge what's "good enough", but if you want top-notch results then the "entry level" solution was the Nikon LS5000, which ran about $1100 new (no longer in production). Many camera stores still have the Nikon or similarly capable scanners, though, so you might ask around. They would probably describe the service as "slide scanning" or "film scanning".