Lot of stuff listed, I did not look them up so I can not say what you really need. Some one else can step in and tell you about all those parts.
As far as needing the Navigation Module, if you want to hear the turn prompts, MP3 songs loaded onto an SD card and installed into the GPS or make/take a phone call using the GPS interface you will need to connect the audio output from the GPS to the Auxiliary input port on the front of the radio.
Now if you don't want to listen to MP3 songs or make/take a phone call from the GPS interface then you have a choice of installing the Nav module or not. The Nav module is nothing more then an interupt module. If you install the module you will be able to listen to any radio function i.e. FM/AM, CD etc. and when a turn prompt from the GPS comes thru the module will interupt the radio function you are listening to and you will hear the turn prompt. After the turn prompt completes the radio will switch back to what ever you were listening to before the turn prompt.
If you do not install the module you can still hear the turn prompts by just connecting the audio output of the GPS to the Aux input port on the radio, but in order to hear anything from the GPS you must have the radio in the Aux input mode. With this setup you can not listen to any other radio function and still hear a turn prompt, you have to be in the Aux input mode to hear any thing from the GPS.
It just depends on what you want to be able to do.
Also in order to make/take a phone call you will have to purchase a helmet microphone interface such as the HD Bomm or equivalent.
Hope this helps you out a little bit.