Using Adobe Camera RAW you are essentially just flipping switches that don't do much till you export the file to a format such as JPEG. Your original capture time, and the EXIF data associated with that original shot will not degrade due to you changing the EV value or similar.
Changes made to the RAW file are completely non-destructive. The only thing that changes is the metadata stored on how to render that image to an output such as JPEG. The original file is left unchanged and intact completely.
Technically Adobe Camera RAW as part of Photoshop has the option to store your camera raw settings in two places, either the Camera Raw Database or an XMP Sidecar File. The Camera Raw database is indexed by file content, so the image retains camera raw settings even if the camera raw image file is moved or renamed(on the same computer). The XMP sidecar file stores the settings in a separate file, in the same folder as the camera raw file, with the same base name and an .xmp extension.(ref)
If you edit a RAW file in an Application such as Lightroom, you have the option to store the changes to a sidecar XMP file. This not only preserves the original RAW file without modification, but frees your images from the Lightroom catalog. You can now move your files around and only bring along the XMP file instead of the entire Lightroom catalog.
Overall, go ahead and mess around with the Camera RAW settings, you aren't going to do any damage.