Hi, no idea why there'd be two - I'd assumed the glo was just a regular touch with a fancier panel - I can't think why you'd want two. I'm guessing at least one of them will give you the root terminal access though. You could test which one by manually holding your pins, or sockets onto the metal of them to check, before soldering.
Soldering isn't hard, but there is a bit of a knack to it. Overheating the board is usually my biggest problem in things like this - if you leave the heat on for too long then sometimes the copper traces lift off the board, and they're next to impossible to make secure and reliable after that. On the other hand, if you destroy your serial port headers then you've not lost much since you aren't using them anyway. You'd probably struggle to do any damage beyond mangling the physical traces.
But it is bulky - even the most compact connector will stick out of the case and be sharp and uncomfortable - if you plan on using the glo as a reader.
I can see why having a hardware serial port would be useful for a change as big as a new OS - I guess it means you don't have to worry about having usb drivers in place right away? Or is there something else that is missing from the usb implementation of the serial port/ethernet?
(and the serial parameters are 115200 8 N 1 - I re-found this on http://blog.ringerc.id.au/2011/01/se...serial-on.html