I've seen someone with no Salesforce experience (But a Java/IT background) pass the 401 after two weeks of concerted study and no Salesforce background so my first suggestion is not to fear it.
Pay attention to the weightings in the Study guide as this translates to question counts and significance in the exam.
As others have mentioned the 'Developer' title is also somewhat of a misnomer as its more an advanced configurator exam (you don't deal with code apart from knowing about capabilities of Apex/VF in general terms).
Finally, the Developer Certification is the doorway to the Advanced Developer Certification which requires much more knowledge in the way of force.com development. This certification will take upwards of a year to obtain given the delays in windows associated with the Assignment and in marking the assignment, so if you want to start that journey, start it as soon as you can :)
I would remark that the certifications are worthwhile as they require you to obtain a much broader understanding of the product than you might get in a single job/organisation.
Reference: I have all Salesforce.com Certifications.