It really depends on how much time you have vs. how much $$ in your budget you have to do your
slide scanning project. It also depends on whether you want archival quality scans, or whether you just want quick and dirty scans as a backup.
Factor 2-3 minutes a slide and more with color correction and dust removal (really important to get all the dust off - and wear gloves if you DIY) and you can get an idea of how long this is going to take you.
There are services that do this - GoPhoto.com is the only
photo and slide scanning service that has a NO-RISK guarantee: they'll scan everything you want scanned (no up-front organization needed), and you review all the scans online and ONLY pay for the scans you want to keep. Other scanning companies allow 0-20% deletion, and most require you to organize up-front.
GoPhoto also scans in the U.S., and has a 1-click port to Facebook and flickr.
If you're going to do it yourself, add up the amount of a good scanner and software (look into digital ICE - you'll need it), and then compare how much you'd pay to outsource, and you can get an idea of how much you'll be "paying" yourself to do it.