There isn't a lot of specific work on navigation in any GUE class that I know of or have heard tales of, but I'll tell you that the increase in situational awareness makes navigation easier, because you are so much more aware of what is going on around you.
As for what you do when one spouse goes DIR and the other doesn't . . . read my posts from 2005 and 2006! The short answer is that my husband thought taking Fundies was stupid, and that it was overkill for a recreational diver. And today, he is a PADI instructor who teaches his students in backplates and bungied backups, and gets them horizontal and stable in midwater before they ever hit an open water dive. He dragged HIMSELF, kicking and screaming and dragging his feet, into this kind of diving . . . because he dove with me and my friends, and he decided on his absolute own that what we were doing was BETTER.
As for what you do when one spouse goes DIR and the other doesn't . . . read my posts from 2005 and 2006! The short answer is that my husband thought taking Fundies was stupid, and that it was overkill for a recreational diver. And today, he is a PADI instructor who teaches his students in backplates and bungied backups, and gets them horizontal and stable in midwater before they ever hit an open water dive. He dragged HIMSELF, kicking and screaming and dragging his feet, into this kind of diving . . . because he dove with me and my friends, and he decided on his absolute own that what we were doing was BETTER.