Hi Shawna,
1) I think the best way to approach this would be to first import your contacts through the "Customer Leads" Table. This way you have the ability to add many more fields you probably want included (billing address, shipping address, CompanyName,…), just don't include or worry about the Tags field at this point. The next step is to manually enter each tag in Method you will be using from your own tag lists. If you need help finding where to manually add tags, follow this link here.
Now that you have added your contacts to the Customer Leads Table and manually added the tags in Method you will be using from your own list, we can move to the final stage. Now you can export (from Customize->Integration Tools) your "Contacts Table" (make sure to include the "TagList" field), also include a unique field so that you when you go to import this back into the "Contacts" table (with your added tags for each user), you can match to an existing record, so there aren't any duplicates.
2) I believe I partially answered this question from my response to question 1. The best way to import the different fields would first be to add as many fields to one file as you can. Also from my answer to question 1, you can import to the Customer Leads Table which allows you to enter most of your fields. However, if you require to add additional information, you can export the "Contacts" table, add certain areas to your records here, then import back to the Contacts Table.
I hope this helps explain this a little better, just reply here if you still require any further clarification.
- Ben