Replacing a particular word with another word in all the xml's under a particular directory with sed

Hi Folks,

Could you please advise what will be the SED command to replace a word in all xml's under a particular directory
for example let say I rite now at the following below location

$ cd /ter/rap/config

now under config directory there will be lots of xml file , now my objective is to first reach to the config directory that i will achieve , and then in all the xmls where the word TTT is there I have to replace it with CCC so please advise how can I achieve this with sed in unix. Thanks in advance.

Show the input you have and the output you want. If you can guarantee CCC will not appear inside tag labels, etc, it's easy enough, but if it appears in tag names etc and you don't want it substituted there, it gets trickier.