Please read the docs from start to finish one more time.
The location of the resource file is defined in the main config file.
nagios.sourceforge.net/docs/1_0/ ... ource_file
The resource file is used to store macro's.
If you look at the checkcommands.cfg file, you will see that all checks start like this...
$USER1$ is defined in the resource.cfg as /usr/local/nagios/libexec
All plugins are located in that directory.
So check these and make sure they are correct, then config your services and hosts.cfg files, and bam, you are good to go.
Again, you appear to have skimmed over the docs much to quickly. It would help if you went through them, line by line, and understand each and every one, so that you can grasp the entire concept more easily and make nagios work it's tail off for you.