I have never used HBPC, but I assume I can "somehow" save my data from my 798 to an SD card and then take the card to my PC, (do all of the HBPC set up stuff) and do all of the work on my PC using only the SD card? Does this sound correct?
That's correct.
Unit:
Insert SD-card in write-mode.
<menu><menu>, go to NAV tab, then select Waypoints,Routes,Tracks
Options, Select All and . . . and Export
Download HumminbirdPC from your Humminbird account(4.3.8 is current version) and install.
HBPC can download your Navdata from the SD-card from above.
It will create a file called SD_yymmddx.gpx where yymmdd is the date and x is A,B,C... if you download more the same day.
If you plan on organizing by lake, I would rename this file changing the SD_ for example to FORK_149113a.gpx.
Name however you plan to organize. If you have console and bow units you could rename SD_ to CONSOLE_ or BOW_.
I have console and bow units networked and sharing data. I maintain all my waypoints on my console-unit. They are viewable on the bow. FYI: HB waypoints are shareable, HB Tracks are not shared.
HBPC will allow you to make changes and provide rolling backups on PC. By rolling backups I mean backups that are the Current, Current-1, Current-2, etc.
You can upload HBPC Navdata back to SD-card, then Import into unit. Power-up unit first, then insert SD-card with Navdata.
You do need to be mindful when unit updating on exactly what is being changed. Unit importing will only load new or changed(therefore new) Navdata.