I was able to get the check_disk_smb to work without issue, however I can't seem to figure out how to get the results displayed on the Nagios web page. This is what I currently have:
check_command check_disk_smb -H fileserver -s share -u user -p password -w 90 -c 95 -W domain
I have the host_name field commented out, as that causes a config error.
I have other checks for the host "fileserver", but I haven't been able to figure out the correct syntax to have the smb check show up with the other checks for that host.