I removed the door skins and sprayed them with Lizardskin to quiet down the car a bit. Unfortunately I used up all my Sound damper product on another project, but I had enough of their Heat and Sound barrier to put a good coat on both doors. While it is not as effective as the pure soundproofing product, I still noticed a difference out on the highway. It seemed like the radio was at a comfortable level 1 number lower than before, but w/o a db meter it is pretty subjective.
The panels went on and off in a snap (pun!), took about 10 minutes from start to off per door following the FQ101 instructions. I just printed them up and took them out to the car. Needed #20 and #25 torx bits and the rest just unsnapped like it was supposed to. Reassembly was a bit trickier, it was a bit of a struggle to get the front of the door skin over the front lip, but it came together in the end. I think a guy on the production line could do the job in about 2 minutes.
Google Lizardskin for the details, I am not connected with these guys in any way, just use their stuff and like it. It's not cheap, but looks good and IMHO works too. Cleans up with water easily, and is supposed to cure and be waterproof, but it's pretty dry out here so I can't say if that's true. If it starts to melt off I can just spend another 10 minutes and remove the door skin and wash it all off!
I need to get more sound damper anyway so I will do the other car with that, and re-coat this one too. There was only a 1/8" thick sheet of grey foam on the inside of the inner door panel, that's all. Not a whole lot there, and yes, you can drive with the panels off the car (ask me how I know!). You have to reinstall the door handle and mirrors, but you could remove the inner panels too.
I wonder how hard it is to remove the seats and carpet? I bet there isn't much soundproofing in the floor either, it could do with a coating too. Just tap the side of the Tridion cell by the door handle: it rings like a hollow box, imagine how it amplifies the road noise. Hmmmm.....