Raw, image size & saving. Help

I am very new to shooting Raw. I have a question on PP in photoshop elements 6.0.
This is what I have done so far.
I open up the raw image & then adjust white balance etc.
I save the file as a DNG file, or I can just click the open image button.
It then opens in elements. I then do any other PP.
What I don't understand is the size. When it opens in elements the size is around 14"x10". (this happens in DPP too.)
What if I want to make a 30"x20" print. Can I make a small file bigger by cropping it larger, & putting in 300 for the resolution? Will I loose image quality that way? Or, do I need to custom crop it in the raw processing part? If I do that, then I have a really large file.
What is the best way to accomplish what I want to do?
I hope you can understand my questions.
Thank-you
Kath

Have a read of my printing and enlargement FAQ, the link's in my sig

So what I am understanding & seeing is that the pixels are the same , even though the jpeg says it is 54"x36" & the raw says 14"x10".
So when I crop to the correct size for printing & put in 300 for resolution, as long as I have that same pixel dimension, I am ok? (ex:3888x2592)

Yep. File size (in pixels) matters, ppi doesn't.