For a location sound mixer making film or TV content, there have been no changes in the rules. You qualify as a Part 74 user.
You have always been required to have a Part 74 license. This has been the case for decades and has not changed. The new rules exempt NON Part 74 users as long as they keep
their power down under 50mW. These users include churches, education, government, bands etc.
Again, for you as a location sound mixer, the rules remains exactly as they have been for decades. Nothing has changed except we can't use frequencies above 700Mhz anymore.
If you want to get your license, you can get the form FCC601 from:
You will also need Schedule H and forms 159 and 160 (also found on the above link).
(four forms in total)