The previous posters are correct. I just wanted to restate the answers and flesh them out some.
You can find the ringtones in the folder /system/media/audio/ringtones. The ringtones are here individually. If by "cleaning up" you mean get rid of tones that you're sure you're not going to use then you can go ahead and delete some. But be aware that you're not really going to save a lot of space. Deleting the whole lot of included ringtones will yield you only 1.2 mb in saved space. You also have to have root access and a program that can delete it for you to do that.
You can add ringtones very easily, just make a folder in the root of your sd card named ringtones and place the ringtones there. The same can be done for notifications. I'm coming from 5 retired blackberries (blackberrys?) and miss my blackberry ringtones and notifications so I've placed my preferred tones in the appropriate folders. My daughter is miffed that my android sounds like my old blackberry but I like the familiar tones.