After dukeala left a comment telling about a blog by Jaanus on the skype website, I decided this would be better edited to include that link. Using what the blog describes, there is no need for a hex editor of any kind.
As wriiten by dukeala,
"...you do not actually need a Hex editor for that, you can simply create, edit and load your own language file - you can read about it at http://share.skype.com/sites/en/2006/11/customizing_skype_with_a_hex_e.html "
As you can see, instead of going through all the trouble using a hex editor, there is an easier way to do it.
While it is almost certainly against the Skype ToS to do so, I thought I would post this as a proof of concept. Do not do this, as it is against the ToS. This is offered for educational use only.
Also, this is my first Instructable, so feel free to rip me a new one in comments ;-)
Step 1: Obtain Needed Software.
A Hex Editor: I used http://www.chmaas.handshake.de/delphi/freeware/xvi32/xvi32.htm
Step 4: Open and Edit.
Now, the best thing to do is locate what you want to edit by using the "Find" utility. Either press Ctrl+F or Search -> Find
In this example we will use the "Add Contact" button.
Open up the "Find" utility, type in "Add Contact" and you should be taken to it, the "A" being highlighted on the right.
Now, the thing about hex editing is, if you don't keep the file the same size, it will corrupt (not a good thing).
What we are going to do here is replace "Add Contact" with "Add Homie"