re: bricking the radio
Yeah.... At least I can say I've done 2 different updates for Gracenotes on mine now, a GPS map update and 2 firmware updates, and all went through without failures.
I've seen a lot of temperamental things about the 730N's operation, but at the same time -- I also see where they've gotten it quite stable doing "day to day" things like listening to satellite XM radio, FM radio, adjusting the menu settings or audio settings, or using the GPS from the touchscreen.
I wouldn't be especially worried about bricking it as long as you load the updates from DVDs that you just recorded and know are scratch/dust free. It seems to be designed with that process in mind.
The areas where I trust it less are often cases where I think the processor in the radio might just be too slow/old to handle things well enough, and/or where it doesn't have enough system memory to complete the tasks properly. EG. I've had it behave oddly with some of the MP3 music I've had it play from USB sticks. Depending on the encoding bitrate and other settings, it seems like some songs will stop playing abruptly, a second or two before they actually end. Or if I tell it to play music from my iPod Classic (6th. generation 130GB model) with it plugged into the USB port in the center compartment, it struggles with requests to skip forward or back through a song that's playing.
I too like to follow instructions exactly so I will stick with the DVD method. But man does this sound like a temperamental radio. I'm pretty tech savvy but the fear of bricking this thing is definitely there.