XML Control replace text

I am using an XML Control to read an XML file and transform it to XHTML with an XSL file. Everything works great, but I need to replace some text in the final result. I have limited knowledge of XSLT which is probably where I should be replacing the text anyway, but I thought I might be able to get the text that the XML control is rendering and change it before the page loads.

So, say the transformed XHTML is:
ABC::XYZ

and I need to replace the :: with = to get:
ABC=XYZ

I hope I am making sense.....