Re: RGB to CMYK
Since every printing press has unique settings, and every press operator is different, you're best to stick with the canned Photoshop CMYK profiles. If you know exactly which press will be used to reproduce your images and what paper ink combination they'll be using, then you can perhaps get detailed conversion settings from the print shop or publishing house. Some will provide such information, some will not.
The canned Photoshop CMYK profiles do very well for general work, however, so don't be afraid to use them if they are all you have.