It's not your documents that is the problem, it's the Office applications:
Office 2004 Applications Won't Work in Lion/Mountain Lion
You may want to consider as well:
These two suites are similar to Libre Office but not as current or as well-supported:
And, then there is Apple's iWork suite:
Pages - word processing and layout
Keynote - presentation
Numbers - spreadsheet
Each can open and save Office compatible files. They may be purchased separately via the Mac App Store for $19.99 each.
(Access to the Mac App Store requires Snow Leopard 10.6.6 or higher and an Apple ID.)
Thanks to everybody for the fast response. I purchased Office 2011 with the mini, so once it's up and running I'll have access to the files, right? But I shouldn't bother trying to open them until I've upgraded the Office suite.
Here are a couple of more wrinkles: One of the virtues of Office 2000 is it opened Classic docs. Should I make sure everything is opened and saved as Office 2000 before migrating?
Also, The best upsupported mail client ever made is Eudora. problems migrating from Eudora 6 to Apple Mail are apparently famous, the worst one being losing date stamps on every piece of sent mail. Any guidance?