[CentOS] script question

I can do "simply" search and replace with sed.
However, I want to setup httpd.conf from a script
that changes the default "/" which is presently:

<Directory />
    Options FollowSymLinks
    AllowOverride None
</Directory>

and change it to the following:

<Directory />
    Order Deny,Allow
    Deny from all
    AllowOverride None
</Directory>

How do you do that with scripts? Basically substitute everything between 
the two Directory tags.

Thanks,

Jerry