Break out instances to different ports

We have three instances of Oracle on one machine under the same port (1521). I would like to break the TEST and DEV instances out to their own ports. What needs to be done? It is possible to take PROD down for a short period. However, PROD needs to stay just the way it is with no changes.

Here's our listener.ora config:

# listener.ora Network Configuration File: /app/oracle/product/oradata/ network/admin/listener.ora
# Generated by Oracle configuration tools.

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /app/oracle/product/oradata)
(PROGRAM = extproc)

    )
  )

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = unix18.umsmed.edu)(PORT =
1521))

    )
  )

Here's our tnsnames.ora config:

# tnsnames.ora Network Configuration File: /app/oracle/product/oradata/ network/admin/tnsnames.ora
# Generated by Oracle configuration tools.

TEST =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = unix18.umsmed.edu)(PORT = 1521))

    (CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = TEST)

    )
  )

DEV =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = unix18.umsmed.edu)(PORT = 1521))

    (CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = DEV)

    )
  )

PROD =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = unix18.umsmed.edu)(PORT = 1521))

    (CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = PROD)

    )
  )

EXTPROC_CONNECTION_DATA =
  (DESCRIPTION =
    (ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
    )
    (CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)

    )
  ) Received on Wed Apr 04 2007 - 16:28:11 CDT