Everything should be updated automatically. We haven't shipped any 5.1 CDs for over a year, though, so if your CD is actually version 5.1 and not 5.1.1, you should get the free update from 5.1 to 5.1.1:
www.digidesign.com/download/511
If you run into any installation or authorization problems with D-Verb, the version 1.8.1 update works with either 5.1 or 5.1.1, and can be downloaded from here:
www.digidesign.com/download/dverb.html