I assume the DAN O2 provider course is similar to the BSAC O2 administrator course.
Fundamentally, these are first aid courses.
In my opinion, anyone doing any regular diving should attend an O2 administrator course, and subsequent refreshers. Even more so if you are doing more advanced dives involving extended decompression and mixed gas.
The course will go through diving related injuries, symptoms and first aid treatment. Predominantly, it will be DCI, but also near drowning etc. (First aid for diver related injuries is generally provide 100% O2 and evacuate to medical aid ASAP). There will probably be some AV and CPR exercises as well as O2 enriched AV and CPR.
Within my branch we tend to teach the O2 admin' course bi-annually. Encouraging everyone from Ocean divers (PADI OW) up, to attend, plus all those who have previously done the course. Generally, it's a fun day which ensures valuable skills and knowledge are learnt and refreshed.