Hi Joe, I'm not with Support, but I saw this and thought I'd respond. I use 'Edit' | 'Find and Replace' to change or remove characters or spaces in file names.
1) Open Contact Sheet on image location
2) Select All
3) Edit | Find and Replace
4) Type a single space in "Find" and nothing in "Replace" (to remove it) or an underscore (to replace it)
5) Check only the "Filename" box
6) Click "Replace"
The "catch" is they were all in the same folder, so the images were all viewable & selectable in one Contact Sheet. I haven't tried doing this for images in a folder hierarchy. There may be more elegant solutions involving, say, substring extraction.