Since you've determined that this module is the way to go, this may help:
*.so files are Shared Object libraries (like DLLs)
*.o files are statically linked (like *.obj)

I like to use slocate (i.e. updatedb) to search for missing (header)
files. If you cannot pull this off, then you might search the other
tarball for these files.
If this does not work, perhaps a google or apache search for a tarball
that you might be missing.

Once you discover the location of the missing files, add this
directory as a flag option to configure.

There are 2 main ways to compile Apache: static or dynamic.
Dynamic uses .so files, and is preferred, as modules can be added or
removed with a *.conf change and a restart. Static requires a
recompile, but runs slightly faster.

Don't forget to check the configuration files in the
/etc/httpd/conf.d/ (typically) directory, as well.

Finally, have you tried any docs, such as the howtos?
Happy Holidays, Bruce