After / Upon

After installation of all wooden panels at the site, another two panels were found to be damaged. We need all these panels to be replaced with new ones.

After completion of installation of wooden panels at the site, another two panels were found to be damaged. We need all these panels to be replaced with new ones.

Upon completion of installation of wooden panels at the site, another two panels were found to be damaged. We need all these panels to be replaced with new ones.

Please check the sentences above and advise me which one is grammatically correct and appropriate one?