Is it ever worth using a non-mage character to attempt this order? If so, are there particular character types that seem to have better luck? If so, what skill level is required for a reasonable chance of success?
If mages are the only characters that should ever attempt this order, at what skill level should they expect to succeed?
If you get cont. efforts… it means an artifact in on the ground.
If you get no artifact found it means nothing there.
The above may not be the exact wording but it is close enough.
A non mage doing a 900 can at least inform you if an artifact is present in the hex.
You can pick up artifacts with non mages though I never have really tried outside of picking up starting artifacts in FA or artifacts that I had secreted.
What if a character died in a location from an encounter and dropped his artifacts, would a character of the same nation then be able to do a 796 pick up artifact, or must it be 900 find artifact ?
796 only works if a character of your nation actually used the 792 order to drop the artefacts in the first place.
Hi Scotty
Not sure if you got an awser to your question so I will try to help. The diffeculty of picking up an artifact largely depend on the terrain. Plains being the easiest and deep sea the hardest (I guess). A none mage could pick up an artifact on plain, I have done it but cannot give you percentages on success. It depends on have bad you want the artifact and how short you are on orders in the hex 
Help that helps.