These are hand-picked howtos that explain something about running Nagios+Check_MK with enough bonus info to let the reader understand no just the 4 lines of config for solving a single Check_MK config issue, but also the inner workings that turn 200 lines of Nagios config into 4 lines of Check_MK config.
My site also has a lot of Check_MK howtos that should enable you to run a more fine-tuned setup.
You should not miss the official documentation!
Using Dell OpenManage with Check_MK
OMD Installation and Check_MK Configuration at ORCA / Breakable Experimental Network
From the same site: Using Eventhandlers for automatic Inventory & deletion of KVM VMshttps://geni-orca.renci.org/trac/wiki/OMDeventhandlers
Using Check_MK to monitor the "DTC" hosting control panel
Ignoring services based on advanced syntax with explanations:
Chris Carmichael's notes and howtos. Always fun to read notes from really skilled Windows admins!