Hi Monettevelasco,
I tried to reproduce your issue, but didn't get any issue. I followed the following steps to reproduce
1. Put the sample custom panel in /users/<user name>/Library/Application Support/Adobe/XMP/Custom File Info Panels/4.0/panel
2. Check the File Info in Indesign CS 6 and sample panel was there.
3. Moved Sample Panel from the above directory to /Library/Application Support/Adobe/XMP/Custom File Info Panels/4.0/panel (the same path you have given)
4. File Info shown the Sample panel and there was no any issue
Could you please delete the panel preferences which is in /users/<user name>/Library/Preferences/Adobe/XMP/File Info/4.0/work (Adobe XMP File Info SDK Programmer's guide "Panel Preferences section page: 49") and restart the Indesing and check the File Info?
If you still getting problem with the panel could you please let me know what do you mean by replace? It will be better if you give me the steps you did and get the issue.