A space-faring human is paid/contracted to integrate with a desert people who are VERY in-touch with the desert - a la Avatar?
I remember the desert people were taller and thinner than humans, used Saracen-style Scimitar swords, had their own alien language, and over the course of the book (books?) integrated this man into their society.
He ultimately went native -- I remember this because he would wear their robes, bathe with sand, and shave all of his body hair.
It's a book I read in the early 90's, and I would like to read it again, but my Google-Fu has failed me. :(
EDIT: The desert people are used as bodyguard/mercenaries due to their excellent swordsmanship/fighting prowess and their very strict honor/belief system similar to Bushido. They eschew technology, but are exposed to it enough that space travel is a non-issue. The protagonist is also a space/war hero type person and generally considered an adept fighter until he meets the desert people.
I appreciate any pointers!