Yes, you can replace an episode's audio or video file after publishing it, without unpublishing or deleting the episode.
The episode keeps its existing link, analytics, and position in the RSS feed. Only the file itself changes.
If the podcast has a connected YouTube channel and the episode includes video, replacing the file uploads it as a new YouTube video, so that video's views, likes, and comments do not carry over.
This isn't currently available for episodes imported into Riverside from an external RSS feed.