actually you dont have to mess with the script file at all
privateshopwnd takes that string from sysstring-e.dat so i would suggest you one of these options: 1) edit sysstring file and change id 134 - Adena - to the text you want BUT this probably will also replace Adena string in inventory and some other places - so i rather wouldnt do that 2) edit sysstring file and add your currency name for one of the IDs that arent used, then edit interface.xdat and change id to the one you just created http://prntscr.com/crhaj3