Yes you can copy and paste field definitions from one filemaker Pro 10 table to another. If it's a calculation that references a missing item, you'll have some more work to do. Such problem calculation fields end up enclosed in /* comment */ brackets so you can fix the missing references and then remove the brackets.
If I follow your descriptions correctly, it sounds like option 1 is good for adding new fields to an existing table and option 2 is good if you can structure your database so that your modified fields are all part of a separate related table.
Thanks, Phil - glad the copy and paste will work! Having taken a quick look at the file with the most modifications, it has one table in it, and most of the field calculations are 'internal' - i.e. they only access fields I would be copying into the table, so that would cut down my work considerably.
I've just had a look at the relationships graph, and again I only have 7 or 8 relationships that I have created, so not too arduous.
Value lists are simple as I can copy and paste the contents - unless you know a better way!
Then, fingers crossed, I can import my scripts - can I select only a few scripts to import, and not all of them?
Given the time stripping out an old file might take, it looks as if the first option is good for me.
Not quite the seemless upgrade to a new Mac I was hoping for, but hey...!