the best recommendation i can give is to go around to various shops. check out their portfolios. ask about cleanliness/sterilization. talk to the artist about the design. get a feel for the place. if you don't get a good vibe, move on. you mention that the tattoo is "fairly complicated." tell your friend to keep in mind that not everything that can be drawn can be tattooed. a good artist will tell them why, and offer to help change the design if necessary.
some recommendations in this general area:
jesse tseronis. currently working out of a shop in winchester, va called body of xpression, i believe. about an hour out of town, but worth the drive. 540.327.5337. he's done most of my work lately.
great southern tattoo company, college park or northern va. sandy has done some of my work. they've been around forever.
fatty's custom tattooz. dupont circle. fatty.
ambroto's. silver spring. mike smith.
marlowe ink. fairfax (?). near tt reynolds. james marlowe.
jinx proof. georgetown. tony.
that should get you started.
