Actually, what you want is a DI box. Get a good one, like the Little Lab's Red Eye : (
http://www.mercenary.com/litlabredeye.html ), and you'll have a useful studio tool for years to come.
I'm not sure what kind of effect you're looking for by vocoding your bass, but the answer is "No, you won't hurt any of your gear." So get creative and share your results...