I recently moved back to the OG after serving a year as the MOS MOO. Here some observations and things to consider:
Career broadening is looked highly upon in the Air Force right now.
For non-prior 21As, Accelerated Aircraft Mx Officer Course is a 2 week AFSC awarding course crammed into 4 at Sheppard.
As matmacwc said, you will go BMC as a fighter guy but you still get to fly. I flew 55 times last year.
Mx will have a hard time accepting you as a "zipper suited sun god". To help yourself out, wear your flight suit only the days you fly.
Prepare yourself, take the first two weeks and become intimately familiar with AFI 21-101, AFI 21-103, TO 00-20-5 and ACCI 21-165 plus all the supps. After you are done with those, read the MX 3-3 and Maintenance Metrics US Air Force. Knowledge is key.
Mx is like the Army, rank and position mean everything.
In conversation with other MX officers/sncos I would refer to ops as "them" and Mx as "us". It helped with trust and credibility.
Here is the kicker, AMU OIC = FLT/CC & MOO = DO. Your ops leadership should not let your SURF take a hit when you return. I expect to take flak for this statement. Some of the old heads on here will be better suited to give guidance on career progression and how promotion board members read surfs.
Hopefully this helps. I learned a lot and hopefully it will serve me well in the future.
Standing by for questions or comments.