Are you talking about internet only? I replaced the Actiontec router that Verizon supplied with an Asus RT-N16 running DD-WRT. Many more features and better range. If I were to add Fios TV, then I would need to return to the Actiontec.
It's been awhile since the switch over but I think you go into the Actiontec and tell it to release the IP connection and then power off. Disconnect the Actiontec and replace with your router of choice.