How do i create a stored procedure that has multiple complex parts that include functions?

This is a very complex procedure so I need as much help as I can get because I am new to database programming and need help as soon as possible.
 I need to create a stored procedure that accepts information on the size of the slip desired (slip_size) and produces a listing of the marinas (marina_name)  in that state with slips that size.
Example of slip_size: 100x30x80

Here are the following requirements:
1) the user provides a state(two-letter abbreviation), width, length, depth as parameters
2) determine which marinas are located in the state specified by the user in the parameter. If no marinas are in that state,display a message to the user indicating that TM(the name of the database) does not represent any marinas in that state.
3) If there are marinas in the state, determine if any of the slips in the marinas have a width that   is equal to or greater than the width provided by the user, a length that is equal to or greater than the length provided by the user, and a depth that is equal to or greater than the depth provided by the user.
4)If no slips are found to satisfy those requirements, then display a message to the user.
5) if any slips are found that satisfy the requirements,
    a) display the marina name(marina_name),
    b) marina phone number (Marina_Areacode, Marina_phone) based on this function:

   -- SEE CODE SECTION

    c) display the manager's name(Manager_FName, Manager_LName).

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-- This function is purely for getting the phone number only
 
CREATE OR REPLACE FUNCTION formatPhone(pvAreaCode VARCHAR2,
                                       pvNumber   VARCHAR) RETURN VARCHAR2 IS
   lvAreaCode VARCHAR2(3);
   lvNumber   VARCHAR2(7);
BEGIN
   -- remove trailing/leading whitespace
   lvAreaCode := TRIM(pvAreaCode);
   lvNumber   := TRIM(pvNumber);
 
   -- check for invalid format (wrong number of digits, or other non-numeric characters)
   IF NOT regexp_like(lvAreaCode,
                      '^\d{3}$') OR
      NOT regexp_like(lvNumber,
                      '^\d{7}$') THEN
      RAISE_application_error(-20001,
                              'incorrect format: should be xxx xxxxxxx');
   END IF;
    
   -- format and return result
   RETURN '(' || lvAreaCode || ')' || substr(lvNumber,
                                             1,
                                             3) || '-' || substr(lvNumber,
EXCEPTION
   WHEN VALUE_ERROR THEN
      RAISE_application_error(-20001,
                              'incorrect format: should be xxx xxxxxxx');
END formatPhone;