You can get at most of the currency symbols by just doing some simple find and replace stuff, but there are a few that are hard coded within php or script code that this will not work for. You definitely cannot do a global find and replace since php variables start with the $ symbol.
In general you will need to update this for the cart object, then for the display on the public pages and finally inside of the script for a couple parts. For example if you change the item options when viewing the detail page the new price based on the options will show. This price has a $ in the code for it so you will always see it there unless you change the code reference.
If you have any trouble with any part of this let me know and I can help you get things worked out.