Steinberg's Voice Designer is a plug-in that I've used with Cubase SX 2.0 & 3. The plug-in is a pitch shifting piece of software that is very simple to use. I no longer run this plug-in on my system as I run Pro Tools now, which this isn't compatible with. To be honest, I don't remember too much about the installation process, which is probably a good thing as I think that I would remember if I had any problems with it, so I'm sure the installation went smoothly as it usually does. For some reason I think that the Steinberg Voice Designer has a few different version, but I'm not too sure. Either way, the version that I used to have has a simple interface consisting of only three sliders for pitch, tone, and for mix level. So really you don't have to do too much to figure out exactly what this plug-in is capable of doing. I don't believe a manual is necessary, although I haven't seen one for it so I can't say anything about it's usefulness.
When I used to run the Steinberg Voice Designer I used it in Cubase SX 2.0 mostly, but also in SX 3. You can't run this with any other sequencer if I'm not mistake, as Steinberg makes it for Cubase specifically if I'm not mistaken. I ran Cubase SX with a Hewlett Packard Pavilion dv8000 lap top computer and a MOTU 896 HD audio interface. I can't recall if I ever had a problem in terms of performance, but it definitely wasn't the type of plug-in that I used very often or in many instances at one time. I first used the plug-in about six years ago.
Overall, I really wasn't too big a fan of the Steinberg Voice Designer plug-in. It doesn't sound very realistic in terms of it's tracking, and I really never found too much use for it. While it is kind of cool that you can shift a tone up or down any place you'd like, nowadays they have much more powerful software to do this like Auto Tune and Melodyne. Even if you do have Cubase or another Steinberg piece of software, I don't think I'd recommend searching around to get this as I really just suggest spending a few extra bucks on a legitimate piece of tuning/pitch shifting software like the aforementioned Auto Tune or Melodyne.