install process for sub woofer in 2010 prius with navigation?

i know this has been covered, but i cannot seem to find it.. my girlfriend has a 2010 prius and she wants a sub. i have a kicker 10 with kicker amp that i would like to install. i am pretty familiar with audio but am by no means an expert. i have seen in the past a converter to change speaker wire signal to an RCA signal. is that all i need to retain the factory JBL head unit (navigation)? also where is everyone getting the remote signal. i know i can find one but sometimes its easier to ask. thanks!