First of all, I don't think you have to include mod_php.conf.
The reason you get that error is that the php module is loaded in the httpd.conf.
Check that you have these lines in httpd.conf:
LoadModule php4_module libexec/libphp4.so
AddModule mod_php4.c
If you have these lines you don't have to include mod_php.conf.
And since you have added the AddType..., it should work.
To check if php is running, you can do this after you have restarted your server:
lynx
http://localhost -dump -head | grep Server
About the library thing, its much simpler and just add the library path in your /etc/ld.so.conf and just run ldconfig.