As said, when you install the XNA framework, help documentation comes along with it. To access it, just open-up MSVS, and go to Help > Contents.
If you've also installed the MSDN documentation, you can also find documentation for a lot of other things, too. You may also want to consider checking out the
MSDN website, where they have online documentation for nearly anything you can imagine.
Also, don't feel like you're not up-to-snuff just because you may need help.
Every programmer needs to look up the documentation for something, or may need a refresher for something. I've been coding for 3+ years now, and I use documentation for various APIs all the time, and even look-up keywords every once in a while if I forget what they do, or need a refresher.
There's also a wealth of knowledge, and tutorials out there on the Internet =]
(may I also note that Vector2s, and Texture2Ds are classes/types, not built-in C# keywords =P)