I hope i'm posting this in the right place and that someone will actually reply (last post was a week ago)

but in short:
>I'll be backpacking Europe from 6+ months.
>I'm a huge photo geek so there will be a lot of photos being taken with my dslr
>looking to purchase a tablet (deciding on ipad mini or nexus 7) to be used for:
---keeping in touch back home
---entertaining myself while on the move
---storing all the photo's i take.
---possibly for navigation around the cities

my questions are:
>how easy is it to move photos from a SD card to the tablet? then from the tablet to an external HDD? (on the ipad mini, photo booth opens automatically with a select all option to transfer once the SD card is connected.)
>am i able to connect an unpowered external HDD (320gb) to the device and run it while i'm on a train or something?
>does the nexus 7 have inbuilt gps and can it run maps and positioning offline?