Like many a cheap car, my Mazda5 is a little noisier inside than I would like. I’m assuming this stuff would be a solution to this problem, but I have a few questions. First, of course, is whether this stuff actually works...

From what I’ve read, the best bang for the buck is to do the firewall, the front doors and around the driver and passenger seats, with diminishing returns from doing the rest of the vehicle. Is this accurate?

Since I really hate crawling around under the dash, I would prefer to outsource this to someone else to do, which I assume would be a car audio shop. What would be the expected cost, parts and labor, assuming the coverage as detailed in the previous paragraph?

How heavy is it? It’s not like my car has a whole lot of power to spare, so I’d like to keep the weight increase to a minimum. Is the additional weight worth the noise reduction?

I just want a quieter, more relaxing car. In the past I used to do all sorts of crazy audio systems with multiple amps and crossovers and equalizers and stuff, but these days I’m content with the factory head unit and the upgraded Polk speakers I installed (although I still want a sub). I plan on keeping this car forever, so making it a little more comfortable and livable are my main goals, and if it makes it a better listening room because of this I will have no objections.