Digidesign's DigiRack Chorus is a stock plug-in found in most, if not all versions of Pro Tools. I've had it running in both Pro Tools 7 and 8, and I'm not sure if this one goes back to earlier versions, but I would guess that it does. You don't need to take any actions to install the plug-in, as it will do so when you install Pro Tools initially. As far as the configuration of the plug-in goes, it's got parameters for gain, mix, a low pass filter, delay, LFO rate and width, and feedback, so there is definitely a good amount of control over your sound here. A manual isn't necessary, and I'm not even sure if there is one.
Right now I'm running this plug-in on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor with 4 GB of RAM. I'm running it in Pro Tools LE 8 that runs with a Digi 002R, but like I said I've also used it in Pro Tools 7 before I upgraded. The Digidesign DigiRack Chorus plug-in definitely isn't one that will take up much of your processing power. It is designed to run well in all systems that are capable of running Pro Tools LE...
I can't say that the Digidesign DigiRack Chorus plug-in is my go to chorus plug-in, but it is definitely nice to have as an extra to the Pro Tools software. For those users who don't have any other chorus plug-ins, this is even more helpful, although Pro Tools 8 users will have the AIR Chorus plug-in as well. While this isn't the most realistic sounding chorus plug-in that I've got in my arsenal, it will definitely get the job done more times than not. If you aren't at the point where you need to buy a chorus plug-in, Pro Tools users should definitely just stick with the DigiRack Chorus plug-in. However, if you're looking for something to use often, I'd recommend getting something with more thickness and overall a higher sound quality.