The Neumann PEV is a parametric EQ that very hard to find. I've only ever seen one of these in my life and only got to use it the one time. Since it was already set up and racked in the recording studio that I used it in, I'm not sure what type of connections it has. This is an analog piece of gear and isn't rack mountable in a traditional rack mount.
Using the Neumann PEV is very simple, and as long as you have basic knowledge about how to use a parametric EQ, I think you'll be okay. The unit simple has three bands - one that you can choose the frequency on, and two that are at fixed frequencies at 60 Hz and 10 KHz. That is all that there is to this EQ, so as you can see a manual probably isn't necessary and would probably be quite hard to find anyway.
The sound quality of the Neumann PEV is superb. It is both clean sounding and adds a bit of grit to your sound as well. Neumann isn't known for making outboard gear like this, but if you can imagine what a Neumann mic sounds like and translate that same quality to a piece of outboard gear, this would be it. This isn't to say that tone wise they are similar as you can't really make a comparison like this, but I'm saying that they're of the same high quality. The PEV is suitable for any and all genres and applications as it is a sound that translates well and simply does its job well.
While the Neumann PEV is an extremely hard piece of gear to find, if you are interested in unique and rare pieces of outboard gear, this would be quite a find. I'm sure that the price would cost a lot, but I haven't looked too deeply into the price as these are few and far between. All I can really say is that if you ever have the chance to try out the PEV, definitely give it a shot as I think you'll be pleased with what you hear. Neumann does make a variety of other outboard gear, but the PEV is one of my favorites that I have tried.