This is a sadly absent part of the literature. The bottom line is that he can be successful and overcome his nightmares, though it will probably be difficult to face them. Teach him to turn his nightmares into dreamsigns, but MOST IMPORTANTLY, teach him about dream control first. Or, have him sign up so that he can get on the forums or the chat and talk about it. Teaching him to work hard to become lucid just so that he ends up in a nightmare and either panicking lucidly or losing lucidity because of fear is probably just going to turn him off the subject. Make sure he knows how to control them and turn them around before you start teaching him to attain lucidity.