Dear Spencer!
You may want to pick up a Sony UY-S77, UY-S90, or UY-S100 minilab scanner for under a couple hundred bucks on eBay, a 35mm strip film gate, and/or a slide feeder gate. (Oh, and a SCSI card, too!) This will allow you to chew through the film archives to generate something like "index print-to-4x6" quality images for you to catalog and pick out the choice shots to re-scan on a better scanner.
Caution: If your Father shot a lot of Kodachrome, beware that, just like B&W negative film, Digital ICE (scratch & dust removal via an IR channel, i.e. RGBi), doesn't work due to the silver retained in the image. In other words, when you see a gorgeous 40 year old slide that, when viewed from the emulsion side, looks like it's been etched into the film... That's Kodachrome.
On The Other Hand, if the slides look washed out and have a magenta cast, then they are old E-4 Ektachromes. 

The forums on Photo.Net are an excellent place for scanning help.
Forgive me if this is in the wrong place, but I have questions concerning scanning UW pictures taken with a film setup...
My dad was an avid UW photographer, and I have recently found a HUGE stash of pictures (hundreds) and slides(hundreds) he took over 20 years of diving (1960s-1980s). I am planning on buying a NICE scanner to document and preserve all the images and am wondering if anyone has any suggestions as to the best scanner for the job, and/or advice for getting the best result with prints and slides that have been unceremoniously piled in the basement for 25 years!
Thanks in advance for any help!
Spencer