If you are wanting to replace ALL customer names, you will need a program like xalan - that can perform xsalt. This is what allows you to make these type of modification.

A problem with XML, is that it can be difficult for UNIX utilities to handle - for example
1) Might be one LONG line. Longer than a text editor can handle.
2) Might have Unicode (binary zeroes) which, at least, on my version of UNIX, is difficult to handle.
3) could be formatted like this:
<CUST_NAME>
Tom Cruise
</CUST_NAME>