Your speed would remain at G speed because that is the fastest that router can possablly go. With that said adding a N router as an access point to your Telus router WILL NOT make your network faster. Depending on the placement the best you could do is increase the range of your network.
To increase the speed of your network what you want to do is what was suggested by emerald earlier. Which was to disable the Telus G router (disconnect everything, all ethernet, and WAN connections) and replace it with your new N router (reconnect everything and then configure the network to your liking). Then and ONLY then will your network reach N speeds.
Hope this helps!