|Generally speaking you can't install a router into a network that already has one|
This response is SO wrong I don't even know where to begin.
it can be done in theory but gets very complicated.
Actually, it's quite easy if you know what you're doing.
A range extender isn't a bad idea.
Also, you could use point-to-point antenna's, outdoor AP's and bridges. Something like the following:
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.