You want to split the front end (queries, forms, reports) from the back end (tables). You can do this in a couple simple steps:
(1) Create a new database and import the tables from the existing database into it (use menu choices File, Get External Data, Import). Close that database.
(2) Open the original database, delete all the tables, and then link the tables from the new database you created. You will end up with linked tables having names and data identical to those that you had, but the tables will be "linked", that is, the data for the tables will be found in an outside database, not in the database you're working in. The linking can be done by making menu choices File, Get External Data, Link Tables.
After you do this your dad's database will be composed of a front end database and a back end database. You can make changes to the front end and then just email it to him. (He may have to relink them, depending on whether the database holding the linked tables is located in a directory with the same name as the one you're using on your machine.) The only time you'll have to touch the back end is if your changes require structure changes to the tables.
There's probably lots more information about splitting the databases in the archives or the FAQ's, but that's the basics of it. -- Herb