If your table names and column names conform to Oracle standards and your tables are already properly normalized, you'll have an easy task. Print out the table descriptions and go over the naming standards and the table relationships with the Oracle DBA. He will tell you what needs to be changed. Once you've had that meeting, you can assess what impact this will have on your application.
If you decide to proceed with the conversion, make all the name changes and structure changes to a copy of your existing Access app. The DBA will define the tables for you in an Oracle database. Once the Oracle tables are created, delete the original tables from the Access database (make sure you have backed up so you don't loose any necessary data). Then link to the Oracle versions of the tables. You should be back in business.
If you need to load existing data into the Oracle tables, link the Oracle tables to a copy of your Access db that contains the data tables. Create append queries to select the data from the Access tables and append it to the cooresponding Oracle tables.
I have created many Access databases with various RDBMS backends including Oracle. It is my practice to complete the design and build all the tables in Access first (adhering to the target RDBMS naming conventions). Once the table structures have stabalized, I have the DBA create the new database for me. Then I just load the new tables and link to them instead of their Access versions.
Since I don't have Oracle or DB2 or Sybase at home, I usually keep a copy of the original Access table database so that I can work at home. I copy the front-end which is now linked to the Oracle or DB2 backend and on my home PC, I change the links so that they link to my Access back-end rather than the RDBMS.
As long as you have not had to create pass-through queries or stored procedures and triggers, you should be able to swap back-ends at will in just a couple of minutes.
