Off Topic: Underground Propane Tanks

[SuiteSuccess]

Totally off topic, but need to pick the brains of some of you since the knowledge of this group covers lots of areas.  I live in the country and have a buried 1000 gallon propane tank that is not leaking but might be getting to the end of its service life since it was installed in 2000 and is now 24 years old.  I would assume it is anode protected with magnesium anode bags but cannot find any wire connecting points.  Trinity Industries manufactured the tank but sold off that division 10 years ago and can’t give me any guidance.  I cannot find anyone in my area that can test the bags or has a copper sulfate half-cell electrode equipment to rent.  I can buy the electrode and test myself which is option 2. (YouTube explains how pretty well).  So here are my options:  1.  Continue searching for pro service (unsuccessful after many calls). 2.  Buy the half cell electrode and test myself. ($100).  3.  Just buy new anode bags and attach (need two 17# bags at $350 a piece) 4.  Bite the bullet and replace the whole tank. (~$10,000 including installation).  
Conceivably these tanks are good for 25-30 years underground but don’t have any previous experience myself to base that on.  So any suggestions/ help from anyone with experience?