Hi
I picked up a M274A5 at the end of last summer. I too, am a novice. There are lots of great mule owners out there that seem all too happy to help a newbie out. G503 Forum has a large mule community.
I knew next to nothing when I jumped at the chance to buy mine. My main guidelines came from previous experience in mvs. Body and drivetrain are number one. Missing parts can be expensive or difficult to obtain.
I bought mine sight unseen, except from a few pictures exchanged via emails. When I drove 15 hours to pick it up I was not disappointed.
To sum up a mule purchase, I would suggest the following as some basic guidelines;
-clean straight deck without dents, extra holes, damage or corrosion
-intact data plates
-all cover plates in place on the deck (Round armament cover, engine cover and brake cover if applicable)
-correct in place engine guard on rear
-good rims
-no visible damage to undercarriage
-all covers on engine
Mules typically have all sorts of leaking seals and gaskets which are easily replaced and not too expensive. Engines are available for around $1100 rebuilt or you can do it yourself quite easily as well. The mechanicals on these are relatively straightforward. There are lots of bits and pieces that appear to be quite cheap until you start adding them all up! Hence, the necessity for completeness. You can buy a nice runner typically for around $6000 to $7000 although I have seen many lately going for much more, as high as $10g.
I purchased mine, unrunning for $2000 and have about $4000 in parts into it including a rebuilt engine, but I am going for a complete factory restoration.