No, absolutely do not change those. This is an area where GEDCOM desperately needs updating. The spec limits media “FORM” to bmp | gif | jpg | ole | pcx | tif | wav
Thankfully kiwitrees is happy to accept any of: ‘avi’,’bmp’,’gif’,’jpeg’,’mp3′,’ole’,’pcx’,’png’,’tiff’,’wav’,
If you have any media with just an empty 2 FORM. then yes, you should fix these. The easiest way is to edit them, but you can edit then reimport the GEDCOM manually if you prefer.