All depends on how deep you want to go.
In no particular order.
1. Examine all BNC and Hirose connectors for corrosion. Fax all lines of course.
2. Clean and lubricate arm trunions one at a time. Can't write out the whole procedure here, if you want to do this PM me, I'll find the document.
3. Clean and lubricate the gimbal bearings. The EFP gimbals weren't killer anyway, and the new owner will very likely be buying this system to gut the sled and make it fully HDSDI and new power wiring. In which case, find out of they're buying a hot new gimbal and save the cleaning/ lube effort.
4. Check to see if the arm cables are straight or twisted and if they are fraying at all.
5. Is the Anton/Bauer mount snug?
6. No offense if this is obvious, but build the rig and put it on and fly it for a few minutes. Is the vest okay? Any plastics cracked? How does the arm feel and sound, etc.
Good luck with the sale. Were I looking for a lighter weight rig for not a lotta $, I'd jump at an EFP. In fact, that was my first sled when returning to Operating. Robert Luna can upgrade the springs, but check with him to make sure that the dog bones are in fact the same spec and thickness as IIIA arm dog bones. I cannot remember if the EFP arms ran "thinner".
No idea who in Chicago, or anywhere else, does this kind of tune up and repairs. As I mentioned above Robert Luna is the gold standard for those kinds of arms. He actually BUILT and calibrated that arm for Cinema Products. He is The Man.
Peter Abraham, S.O.C.