Alan,
Don't take it personally. As you are already aware, it's a complex property and as such requires an appraiser that has experience with these types of properties. Otis is only pointing out to you that if you have to ask "where do I start?" you might not be qualified to do the assignment on your own.
You didn't state the purpose of the appraisal so I don't know if it's for mortgage lending, estate, or something else. The purpose may allow different options on how to proceed.
If the purpose is for mortgage lending and you are using the new form then you need to review the certs because they don't allow for "learning as you go." If it's for another purpose than disclosure to your client (I'd recommend you get it in writing), and documentation of the steps you took to become compentent maybe enough. Another alternative is to look for someone to mentor you through the process.
Having done a number of historic properties I can tell you that a week is probably not long enough to complete the report. In my market there are signficant differences between historic homes that have been renovated and those that have been restored. It is not unusual to use sales that are older than 12 months and farther away than typical. Sometimes historic properties have a regional market instead of a local market, which opens a whole other can of worms.