Does anyone know anything about Native American regalia?

Try to use an App like Google Lens. Use it to take a photo of each item and it will may provide information about each piece. Youre correct in using the term regalia. Dont call it a costume...its offensive and demeaning . The Native Americans in my State prefer the term Indians. Makes sense since they were here before there ever was an America. I think it just reminds them of the atrocities they endured by the govt...and removes their past prior to their being an America.

My uncle Jack from UC Davis could have helped, but he passed a few years back.

Only thing I can really recommend would be to get in touch with the tribe he is affiliated with to get their thoughts. Personally, I would keep it or send it to a museum outside of the USA due to fear of further cultural erasure.

what tribe is he? I would see if I could contact which tribe he was a member of?

Some of the native costumes are very sought after. To start you could consult a reputable auction dealer to give you a market estimate.

I know the patch goes on the right

Find out which Nation's Tribe he belonged to and contact their Council, sell to them to keep within the culture.