If I went from wordpress.com to self hosted wordpress.org with all the files and plugins on my computer, and lets say all the files got corrupted or I needed to reformat my computer, would my website and files be gone forever?
Export files are copies only. Did you delete your WordPress.com blog or not? If not create a new export file. Do not open it after you create it and you won’t corrupt it. You will then be bale to import it a second time.