You should be nervous.

You're talking about taking responsibility for what, in this modern age, is arguably the most valuable asset of many organizations, the data. If that doesn't scare the pants off you, you're probably not a good fit for the job.

I get nervous about every new job and every new situation in old jobs. But, how do you deal with the nervousness? Ignore it and plow forward? Run & hide? Or, acknowledge it and try to get as much information as you can so you can be better prepared so that you're mitigating the issue without dismissing it? Do that last thing and you'll be fine (most of the time).