Nevermind. I figured it out.

I had to do a little bit of workaround for it to work properly.  Here's what I did.

1.I found the CUI file that was stored in C:\Documents and Settings\***Specific User***\Application Data\Autodesk\Autodesk Mechanical Desktop 2005\R16.1\enu\Support. (You need to show hidden files and folders for Application Data to show up.)

2. Copied acad.mnl, acad.mnu, and acad.mnr from there to a new folder on my desktop.

3. Then I typed in the MENULOAD command in 2008, Unloaded the acad menu, and loaded the acad.mnr (since it's the biggest one). Usually this will give an error. Saying something like the menugroup you're trying to load is the same as the default menugroup. That's because they're both named ACAD. BUT, it's a necessary step. Because then it creates a CUI file.  

4. Next I opened the CUI file that it created in Wordpad and replaced all the references to MenuGroup Name="ACAD" with MenuGroup Name="GARY".  The easiest way to do that is to go to EDIT > Replace... (In wordpad). In the "Find what:" box, type in (or paste) MenuGroup Name="ACAD". In the "Replace with:" type MenuGroup Name="xxxx" where the "x"s symbolize the new name. Make sure you select the two boxes that say "Match whole word only" and "Match Case".  After i did that, I saved the file with the new name. (Gary.cui)

5. Then I went back into AutoCAD 2008 and typed the MENULOAD command again. Once again, I unloaded the acad file, (This will also unload the rest of the menus.) and loaded the GARY.cui file.  All the toolbars, menus, etc were then all replaced with his custom ones.

That might have been the long way around, but it worked. That's the end goal for me.

If you save it as a different file name, it doesn't wipe out anything. It just replaces the original acad.cui file. Which is the one most users customize, not knowing that it's the original file.