Don't feel stupid, you'll get it. 
PP = Post Processing. All digital shooting should need some post processing to bring out the best in any image. I use Adobe CS3, which I bought brand new at a fantastic price for $360. It is maybe the best there is for under several thousand dollars. RAW files are huge, yes, but they hold all the data the camera recorded and with many programs, including one of the best, which came free with your camera, you can edit the RAW files to fix lighting problems and some minor noise issues, then export them to JPG format for the web. It takes time and dedication to learn any program, but digital imaging requires some post processing.
Metering refers to the light meter built into the camera. No, there is no guage or bar graph. The bar graph you see in the viewfinder is for Exposure Compensation I talked about earlier, when in Av Mode. There are either three or four metering modes you can set for in most Canon cameras. You should read the manual to learn about each one. Evaluative seems to be the most useful for all around shooting. It's forgiving and good for almost any kind of light. Instead of a dial or bar graph for the amount of light, you see the numbers in the viewfinder change when you move the camera around to dark or bright spots. If you set to Av Mode and Evaluative, then point the camera at light or dark spots, you will see the numbers on the shutter speed readout change. That's about all you get in the new cameras. In other modes, such as Tv Mode, the Aperture number would change. In Manual Mode, then the bar graph pipper moves.
I use Av Mode almost exclusively, cause it is one step removed from Manual mode. Meaning, I set the aperture I want, the ISO, Metering Mode, everything but the shutter speed. And I do this because I shoot birds mostly, changing light, and changing fast. Too fast for me to worry about messing with dials and switches when shooting. And in Av Mode, I set the aperture. All lenses have a sweet spot, an F/stop where the images are sharpest. I don't want the idiot chip in the camera setting aperture to a F/stop that is soft or downright blurry.
To learn all this, sit in bed at night with the camera and manual and a lens on it. Read the book and work the dials and switches on the camera till you can do it without reading the manual. I hate to admit it, but this is what I did and still do with every new model camera I get. It takes about a week, but I can then set any setting on the camera without looking and while it is up to my face and in the heat of a fast action bird shoot. It pays off, and at night, you go to sleep with all that new info in your head to let the sub-concious work on it during the night. 