Hi orlanda,
There isn't a risk of integrity errors, and if the Excel file was incomplete or incorrect, the import process would detect this an not import anything.
Yes, you can export items to Excel, make changes, and re-import the list as an alternate price list. But you need to set up an export Item Template and an import Alternative Price List Item Template that have matching columns as best as possible - otherwise that Excel management will involve a lot more editing.
You can find a ZIP file on our website (containing a number of import tech tips) following the link
here.