This is the time to get your resume ready. If you've not been involved in the upgrade planning and you've not been given a detailed MOP to execute and you've not even been given a login for the software... And the person who I assume has been planning the upgrade is going on vacation then it's time for you go as well.
Alternatively raise your concerns with your bosses boss.. Since I would also assume your bosses boss approved his vacation knowing that this upgrade was coming they may be less then helpful. Or they could have been lied to by being told you are comfortable with all aspects of the project.
If you're not comfortable, get them to postpone, or ignore it all and get you resume in order. This is one of those red flags for bad companies.
Alternatively raise your concerns with your bosses boss.. Since I would also assume your bosses boss approved his vacation knowing that this upgrade was coming they may be less then helpful. Or they could have been lied to by being told you are comfortable with all aspects of the project.
If you're not comfortable, get them to postpone, or ignore it all and get you resume in order. This is one of those red flags for bad companies.