[Wordeater]

I can't speak of the Decalgirl skins for the 350, but I did have one on my 650 for awhile and the fit was tremendous. The key thing in my experience was to use real care to NOT stretch the skin if you find you have to remove it to re-align it when putting it on. Once stretched, it will not fit properly.
I did read the trick was to dip them in soapy water before attempting to put one on. This apparently allows them to be manipulated a bit and helps to reduce the risk of stretching them. (I understand the skins have channels on the adhesive side to allow the bit of soapy film left to be evacuated) Maybe someone else can chime in here as to the validity of this technique. I did NOT use this method.
The fit of the skin on my 650 was more accurate than I expected beforehand, so if I were to do it again I would just approach it by just lining it up EXACTLY along the right hand side edge. (I'd know how close I had it by the time it approached the the bottom right-hand 'option' button; measuring the distance between the right-hand edge to the first button would give you an exact location to set the RH edge to start)
This way I wouldn't have to remove very much of it to adjust the fit if I needed to, lessening the risk of doing damage. I might also suggest you remove as little 'backing' as possible to avoid having any part of the 'sticky' surface of the skin making contact anywhere on the reader except where you want it in the end. I peeled back some of the backing and cut a little bit of it off with scissors to leave as little of the adhesive surface of the skin exposed as possible. Trust me on this.
I removed the skin I had shortly after I put it on because I didn't like the way it looked. I prefer the 650 'naked'. I also bought a skin with the 'matt' finish, and if I were to do it again I go with a 'glossy' one.
BTW, the skin I had was 'Matrix Code'.
I can appreciate wanting to cover up the 'silver' finish of your 350. Not wanting a silver reader was the main reason I ruled out getting a PRS-950, and I sure didn't want a pink 350.

Hope this helps.

WE

Edit.....in addition, the sole reason I went with a black skin on my black 650 was to avoid seeing any misalignment of the skin around the screen if that happened as mentioned in the post by Ripplinger, and with the Decalgirl skins, you will be surprised at what little bubbles you'll get, unlike many other skins on devices.