Setting up a 3rd party router isn’t a problem, and at the end of the day you will end up with better wireless performance in your home. There are numerous people here who can help you with setting it up as many of them use very similar products and all you have to do is post a query….”How in the heck do I…….?”. Not a problem 
If you have set up the Rogers modem / router already, then you probably have enough knowledge to set up another router as the settings are similar but the router would give you more options to use if in fact you wanted to use them. Basically the plan would be to put the Rogers modem into Bridge mode, whereby it acts solely as a modem, cable data in/out, ethernet data out/in. That is a simple switch or button change in the CGN3 and reboot to accomplish. The 3rd party modem is then connected to one of the ethernet ports at the back of the CGN3 and it then becomes your main firewall/router, supporting both wired and wireless connections. Just like the CGN3 you have to set the main router password and set up the security settings, network name and passphrase for the wireless networks. Fairly simple in plan. From there, you then connect your wired devices to the ports on the router and confirm that your wireless networks are up and running. It would look something like this:
Wallplate….RG6 Cable…..Rogers CGN3…..ethernet…..3rd Party Router …
.....ethernet …..wired PCs or laptops
…..wireless …..wireless devices
The only remaining question is what router to install? The principal choice that you will hear around here these days are Asus routers, specifically the Asus Dual Band Wireless N Router (RT-N66U). That is a dual band, 2.4 and 5 Ghz router that should support all of your current devices, except for any 802.11ac devices. I’m neutral on the subject, but, given the number of people here who use Asus routers, that might be a good choice as they will be able to help if any questions arise. This is where crystal ball gazing comes into play. If you can see yourself buying new devices such as laptops any time in the not too distant future, there is a good chance that it will have an 802.11ac wireless card onboard. If so, you might want to consider stepping up to a higher end router which would be the Asus RT-AC66U or the Asus RT-AC68U. All of those routers use very similar firmware and have very similar, consistent appearances in their user controls. They are not the cheapest, and not the most expensive either, and any of them should give you good performance for several years. My only concern with the Asus routers are indicated in this previous post regarding the use of Broadcoms chipset:
Depending on what level of service you have now and might want to go to, the use of Broadcoms Cut Through Forwarding and Flow Acceleration as indicated in that post may never become an issue that you have to deal with and you would have full use of all of the functionality built into the router.
Hopefully this will clear up some of the questions you might have.