Moe,
The simplest way to do this since you need to specify a target URL in the goal (Exact Match goal), the best thing to do would be to have the end of your survey, on the thank you page, add ACTION > Browser Redirect to a unique URL on your website. That URL is what you would specify in the goal, and it would easily track then when users reached that page, and they would only get to that page if they completed the survey.