SkipVought,
iGuidance 4 doesn't have a facility for importing addresses. The PDA version I believe is able to use addresses of your contacts in Outlook, but that's all.
When a destination is added to "Favorites", a data file is created in C:\iNav
iGuidance\Maps (going by the memory here). The data file can be opened in a text editor, such as Notepad. You can see what's there - it's been a long time I looked at it, and I don't remember if the address is there in plain English. If yes, then perhaps a workaround solution could be created - but likely not, since I haven't heard of anyone who has done it.