Yes, it is perfectly valid to reinstall it. Looks like Dell is pointing to use the evaluation media to reinstall it so there should be no problems.
https://www.dell.com/support/kbdoc/en-us/000178353/dell-poweredge-how-to-download-the-microsoft-windows-server-media-iso-file
After installation you can convert
Dism /online /Set-Edition:ServerEssentials /AcceptEula /ProductKey:12345-67890-12345-67890-12345
--please don't forget to Accept as answer
if the reply is helpful--