Talk therapy would involve going to a professional with the idea of changing things for the better (maybe changing the way you perceive your PWS or strategies to deal with people staring or someone that you like who is seeing an extensive PWS for the first time). In many states, talk therapy can be provided by a number of different types of practitioners.... anything from a licensed social worker to a psychologist.
Something more aggressive might involve both talk therapy and drug therapy (something to treat depression or OCD or the like). In that case, you would need to see a psychiatrist.
Check with your insurance to see about coverages as well before you call anyone. Ask your primary doctor for references (actually, truth be told, I always ask my doctor's NURSE... she will be more likely to tell me the truth about whether she likes a particular doctor.).
Check back in soon and let us know what your plans are and how things are working out for you!!