I never tried using a uSD card on it, so can't comment on that . . . I'll remember to update firmware without the uSD in it for next time . . .
I don't know how their firmware update works, but I can see #2 being an issue if it corrupts something . . .
I used a FT232 serial to USB adapter when I did it. I couldn't find a SGC version of the item I wanted sold in the US, so I didn't have a choice but to update the firmware. After I figured it out, it was pretty easy and painless for me. It's a 5 minute process, but it took me an hour my first time as it was non-obvious how to do it . . .