Harold,
Yes, I would recommend formatting whatever card you want to use in the 661 (Utility -> #7). Not just the first time you use a card, but before every show that I go out to record.
In regards to the "load settings" and "save settings", I never use either of those. Those commands are only there if you have a recording setup that isn't saved to one of your presets. what you can do is "save" all of your recording settings to the SD card, and then at a later time, "load" the settings from the same SD card to get back exactly what you need. But if you format that SD card, you'd lose the settings saved to it anyway (because formatting a card deletes everything from the card in the process). Also, I find that the three pre-sets cover just about every situation I need to record in, and it's easy enough to modify the settings if I need to. So no need to save the settings onto a SD card.