CSV Import Options

Hi,

I already have thousands of products in my marketpress store.

I have a csv with thousands of products, some are already in the marketpress store and some are not.

I'd like to import all of the new items into marketpress.

I don't know of any easy way to find and separate just the new items, so ...

If I upload the csv that has some SKUs already in the store.

1. Will the old items be written over or skipped?

Thanks