Data mapper - need to map an dictionary of values to a model

[Luke]

I am writing an order management console. I need to create an import
system that is easy to extend. For now, I want to accept an dictionary
of values and map them to my data model. The thing is, I need to do
things to certain columns:

- I need to filter some of the values (data comes in as YYYY-MM-
DDTHH:MM:SS-(TIMEZONE-OFFSET) and it needs to map to Order.date as a
YYYY-MM-DD field)
- I need to map parts of an input column to more than one model param
(for instance if I get a full name for input--like "John Smith"--I
need a function to break it apart and map it to
Order.shipping_first_name and Order.shipping_last_name)
- Sometimes I need to do it the other way too... I need to map
multiple input columns to one model param (If I get a shipping fee, a
shipping tax, and a shipping discount, I need them added together and
mapped to Order.shipping_fee)

I have begun this process, but I'm finding it difficult to come up
with a good system that is extensible and easy to understand. I won't
always be the one writing the importers, so I'd like it to be pretty
straight-forward. Any ideas?

Oh, I should also mention that many times the data will map to several
different models. For instance, the importer I'm writing first would
map to 3 different models (Order, OrderItem, and OrderCharge)

I am not looking for anybody to write any code for me. I'm simply
asking for inspiration. What design patterns would you use here? Why?