Router to Router

> I am looking to run 2 M60 routers [...]

   What's an "M60 router"?  "MR60"?  Look for "Model" on the product
label.

> My question is that 2nd router. Will it just hook up? [...]

   You'd need to connect the cables.  Whether the second router would
then configure itself appropriately depends on how you do things.

   One plausible arrangement would be to configure the second router as
a wireless access point, rather than as a full-function router.

   Visit http://netgear.com/support , put in your (actual) model number,
and look for Documentation.  Get the User Manual (at least).  Read.
Look for "Set up the router as a WiFi access point".

> [...] I tried something similar [...]

   Thanks for that detailed description of those devices, and how you
connected and configured them, and what happened when you did whatever
you did.

> [...] can I put that 2nd M60 into AP mode, [...]

   See above.

> [...] and it will still run the WiFi that the main router is pushing?

   I don't know what that means.  The MR60-as-WAP will establish its own
"WiFi", but the devices which are connected to it should be on the same
LAN subnet as all the other LAN devices.