Here's another way to skin this lat/long problem:
I've used the measuring tool on the F5 screen to connect the hacture marks N&S and E&W. (The hacture marks, btw, are at 1° interval) I've labeled Lat and Long. Now, to figure out what my position is...you can click 'n drag the measure tool from the appropriate Lat/Long line to your boat then do the math, i.e., kilometer x 0.54 = nautical mile to determine your actual Lat/Long in SHIII. It's close enough for Govt work.
Navigation doesn't have to be that precise to find your way around a flat ocean.
cheers,