That doesn't mean that Ruby is so compact that it's impossible to get a large code base in it. When Ruby projects get large making changes to the code is both painful and scary (I would know since I've had to do just that).
Is your codebase well covered by tests? Do they still run after the change? Did you write tests for the change you just made (preferably before the change)? If you answered yes to all these questions, fear not. You are every bit as covered than you'd be with a Java codebase and you probably have the afternoon for code review.
