learn me running a web forum

I am in discussions to take over a dormant enthusiast website and I am not sure what I am getting myself into. It was built on the MYBB platform. I am not sure what freedom I will need to make changes, such as adding sections, adding or removing members and administrators, and changing the layout. I presume I need to be the administrator to do all that, but I feel the owner of the site is attached enough that he will just offer me to be a moderator rather than hand over full control, despite no longer visiting or promoting the site. Please enlighten me as while I am very good at typing unwanted opinions, I know nothing about running the other end of the site. 

If you're going to be more than a moderator you'll need administrator permissions, and if you're going to be doing any maintenance it would help to have some basic proficiency with a LAMP stack for doing upgrades and backups.

I suspect some of the good people who run the GRM forum could share some wisdom.  Also, the job of running a forum is exacerbated by forum members who do a good impersonation of shiny happy people.

The potential issues with this one would stem mostly from grumpy old men, so reasonably manageable I expect. 

And I have no idea what a lamp stack is.