Does this Fit have a differential? If so, how often should the fluid be swapped out?
Or is it part of the tranny?

 

https://www.hondapartsnow.com/genuin...n=pd:3468341,1

looks like we have it

 

It is part of the transmission, as in every front wheel drive vehicle.

 

Read the owner's manual:

http://techinfo.honda.com/rjanisis/p...AT5A1717OG.PDF

 

Thank you all for helping me to continue my ever evolving understanding of automobiles.

 

What is important, it shares the same compartment with transmission, so there is no separate drain and fill plug for it
On FWD (A/T only) Toyotas from 80's and 90's the differential compartment was isolated from transmission portion (but used same ATF DIII fluid); there are 2 drain plugs on the bottom: one on the pan, one under the final gear.
The differential fill plug was hidden form incompetent mechanic and was facing the firewall. So these big specialists with a little brain (not willing to consult manual before proceeding) drained both compartments but filled up only transmission portion (via dipstick); you can imagine what was expected next:

Grenaded differential
The issue is aggravated because no one bother to measure amount of drained fluid (in which case the technician would notice that they drained far more than needed to be put back) !
Sorry for Off-topic!