Yes we can import your sales history. We're limited only by what Amazon makes available - we can often import 6, or 12 months of data, and I have seen data go as far back as 3 years before.
You can check in you Amazon Seller Central account to see how much A2X will be able to fetch. These instructions relate to finding missing settlements, but it's the same for pulling in historic settlements, have a look and check what you see in Seller Central under Reports>Payments>All Statements:
Confirm that the files are in V2 flat file format or raise a support request to have them changed. Then your full history will be able to come into A2X. See article on How to request history from inside A2X.