The only grammatical correction I would make would be to delete to, but the sentence does need punctuation after professional. Semicolon or em dash is probably your best bet there. As for look vs. looks, I would positively prefer the former, singular form, even though the plural form might be more familiar: one’s looks refers more to the gifts of nature (high cheekbones, straight nose, that sort of thing), where one’s look refers more to an ensemble of clothing and accessories, with coiffure and grooming being somewhere in between or shared. And with that distinction in mind, look seems a better match to the advertisement’s intent.
Attitude should be professional; look need not be.
Note that even with singular look, the modal expression need not does not become needs not—it is subjunctive, not indicative, and as noted and shown it governs a bare infinitive, not the kind with to.