Need to transfer files to remote site using pi VPN

[Bosse_B]

I have set up OpenVPN server on a Pi B+ which I have left at my daughter's home so I can connect to her network.
I planned on doing some file transfers over to her (grandchildren movies and such) using a network disk attached to her router. But now it turns out that the router is an Apple Airport and it has a totally proprietary way to connect to that disk from Apple devices so I cannot use it from my Windows system....

So now I wonder what would happen if she connected a small 2.5" portable disk to one of the USB connectors on the Pi?
1) Would it choke down the Pi power-wise?
2) If not, would it auto-mount?
3) Then if so how could I access the disk so I can transfer my files via VPN?

I can use PuTTY to manage the Pi via the command line interface over VPN just fine, but I have never added a disk to a Linux system before so I do not know the implications.
Is there something I can do there in order to make the attached disk available to my Windows Explorer?

[Bosse_B]

I should add that I have looked at a number of samba tutorials so I know how to set up the service.
However, I would like for the Pi to publish whatever disk is inserted into USB as the DATA share, so my daughter can insert whatever disk and it will be accessible afterwards via samba.
Is this possible?