APEX can create a table Application Programmatic Interface (API) for you. A table API is a package that takes care of the DML, rather than having to implement DML yourself. So you will get a package that you can use to insert, update, delete, or retrieve data from the concerning table. The APIs can be referenced from within APEX, so you can call the API from a PL/SQL region. In this way you can keep the database and the client interface separated.
Make sure you have access to the table
APP_DEALERS and that this table has a primary key.