Question RE: increasing sort_area_size

I am new to the business of Oracle DBA work. A very capable DBA just recently left our company and I was chosen to replace him. We are running Oracle 7.3 on an MS Windows NT 4.0 platform. I ran a tuning report script I got from a book, and it tells me that I am executing only a little over half of my query sorts in memory, with the rest obviously being done on disk.

The report suggests that I increase the SORT_AREA_SIZE parameter. After investigating, I found that this parameter was not specified in our INIT.ORA file. Here are my questions:
(1) Some Oracle documentation that I have read tells me that the
INIT.ORA file is only read by Oracle when the database is first created, not when it is started up after a shutdown. Is this true? Is there a way around this (I noticed that in Oracle Instance Manager, this parameter seems to be editable, and help hints that it will be commited to the init.ora file the next time I stop and restart the database)?
(2) What should my criteria be for determining the new value for this
parameter? I have not found any information on this subject in the Oracle documentation.

I have included the pertinant section of the tuning report below:

########################################################################

Sort Memory Contention

Goal: Mimimize sorts to disk

Corrective Action: Increase sort-area-size

Type                 
Number                                                    
---------------
------------                                                    
sorts (memory)        
3,034                                                    
sorts (disk)          
2,567                                                    

########################################################################

Thanks in advance for the help!

-- 
Steven W. Shaw
Programmer/DBA - Pacific Ridge Data Resources (http://www.crem.com)
work: sshaw_at_crem.com
home: sshaw_at_west.net