You could add coditional code to product_listing.php that would test for the category id = whatever it is, and skip the price and output the release date if true; otherwise output the price and skip the release date. This would require adding a term to the SQL query in (I think) main_template_vars.php to fetch the release date if it exists, and process that into the listing array. Then you would have the data to use in output if needed. Use the upcoming products code to see exactly how to fetch the release date.