Questions about MVC in Javascript and in general

Questions about MVC in Javascript and in general

First, I would like to ask some very basic questions about MVC in general.
Simple questions, but can't find any good answer for them.
Is MVC useful for a one man project, or is it only needed, when more
people work on a project to make it easier to co-op?
How big a project needs to be, to make good use of MVC. I hear everywere
that I should always use MVC, but even for big projects it looks like an
overkill. I can't imagine how big something would need to be, for all this
overcomplicating to pay off.
I have made a single player rpg that is pretty short, and I am trying to
turn it into massive multiplayer. It is all for educational purpose only.
So I was thinking to redo it with MVC, but even though it has a lot of
functions and data to process it still looks way to simple and clear, to
bother with MVC. Maybe if I am making so small projects that I can't see
the benefits of using it, I just shouldn't use it?
Will using all the MVC additional code slow down my app in visible way?
Now about Javascript, there are some solutions for MVC avaliable. Are they
worth using?
Thanks