Hi,
You can edit the form, but with a caution.
For example, if you change the name of a page or subform, then the data structure of the returning XML data/files will not match the editted form.
If you delete an object on the form and import the returning XML data, then the data for the deleted item will be ignored.
If you add an object to the form and import the retirning XML data, then the new object will be left blank, because it does not have a matching node.
If you change the binding of an object (see Object > Binding palette) then this will have an obvious affect on the data import.
If you are just editing captions and static text, then that wont have an effect.
I would be inclined to do a test on a separate test distributed form and then go from there.
Niall