Depending on the model of router, you should be able to use any cable. I have heard that some routers, including commercial ones, have trouble handling the differences between crossover/patch. If it were me, I would just wire a crossover cable and call it good.
As for what needs to be turned off, you definitely need to turn off the DHCP server, any type of natting (or you will double NAT and that would be horrible to troubleshoot), firewalls (your company should have one of these in place anyways). What model of router are you hooking up? Are you using any network switches?