how do i find apache conf files ?

["Jonas C. Drewsen" <jcd@solit.dk>]

    Hi

I am making a package that needs to add something to the configuration
files for apache when installed. My question is :

1, how do i make sure apache is installed ?
2, how do i find out where the configuration files is ?

I'm a bit of a newbee, so I hope someone can help me out here.

Jonas