$130 for a one off update is a pure rip-off, I'd maybe pay it if it was for lifetime updates.
On the other hand, I paid $1400 for the Head unit, even TomTom bundles free updates for life with their products.
Panasonic's latest map, guarantee only last for 45 days after the first GPS fix the unit gets. If you try after this period you will need to purchase the map updates. Sorry for the bad news, you may want to look at the development thread for the cracked maps process.
You can adjust the voice guidance volume from within the Nav app, it's under region I think (same place you choose the voices) plus there is only 1 voice that does the street names. I lost a few voices on my unit when I did the update to 1.05, very annoying.
Thanks for the responses guys:-
@whatiswhat - I'll wait till I need to do a major map update before undertaking that task and hopefully there will be a video tutorial by then.
@Huddy - I did update my maps and lost the voices, tried your suggestion but could not find them in Naviextras