Said

It's perfectly possible but you would need to have setup SSH/VPN access first. In addition you would need to have the ASA interface that you want to configure as a DMZ interface already patched into a switch and you would probably, although not necessarily, need access to the switch.

If you don't already SSH access setup then unless you can connect through the ASA onto a router/switch inside the remote branch and then connect back to the ASA device you would need to visit the site, or talk someone through setting up SSH.

Jon