Podcasts are unique in that they don't have a (90sec or 30sec) preview on the store - the preview functionality just plays the entire episode.
What you want to do with the JSON result you just got from iTunes is parse the "feedUrl" from the results. When you crawl the feed of the podcast directly you can get the audio URL for each episode.
iTunes doesn't host the content for podcasts like they do for songs. The podcast owner is responsible for hosting and pointing their feed to iTunes. Any broken audio links or issues with the feedUrl will be the responsibility of the podcast owner.