1) Use "dishes." "A range" is singular, but what is it a range _of?_ More than one dish.
"Dish," meaning a kind of prepared food, is an ordinary countable noun. Turkey is my favorite Thanksgiving dish. Turkey and apple pie are my two favorite Thanksgiving dishes. At Thanksgiving, we had all the traditional Thanksgiving dishes. We had a total of six dishes: turkey, stuffing, sweet potato casserole with marshmallows, cranberry sauce, apple pie a la mode, and pumpkin pie.
2) Use the definite article before the world "interview," and use the word "an" rather than "a" because "interview" begins with a vowel sound. Don't capitalize either the word "employer" or "interview," because they are not proper names. If the sentence is the title of an article, then use one of the two styles: a) the style used in main titles of important works, like books, in which you capitalize the first word and every important word, including "impress:"
How to Impress an Employer in an Interview
A style sometimes used in subheadings or magazine articles, in which you capitalize the same way you would capitalize in a sentences:
How to impress an employer in an interview