a) the struts probably should be inspected and changed oil at least 5 years. Its easy and probably no parts needed beyond a $0.50 o-ring.
b) leaks out the bottom of the ESCO are likely just the bottom o-ring as it is under deforming pressure and the other seals are not.
c) the Ong debongers for the Legacy do make a difference on the ground. It feels more like a car versus a solid strut when taxiing.
d) there's nothing in the strut that would make me think it can't be inspected and checked in the hangar by any owner equipped with photos, jacks, instructions, time and nitrogen. I would see no reason to change the internal seals unless damage was evident (except for the bottom o-ring). Cleaning, inspecting, changing the oil and putting it back together is probably a day job.
e) Owners should have a set of instructions like this for continued airworthiness along with the part numbers for repairs as may be necessary.
STEPS TAKEN
1) In this photo, I simply dropped the wheel from the strut, leaving the brake lines and brakes attached. I marked the alignment (toe-in) first because you will lose the alignment after the wheel is dropped.
2) depressurize the strut. Drop the strut core by removing the 4 bottom hex screws. Its a mess. My oil was dirty and foamy and not nice. I had 780TT and about ten years on the struts. I did not fully disassemble the inner strut which would be an additional step.
3) Remove the side rails held by 5 hex screws up the side of the strut. They were in perfect condition with no wear at all. They will last forever, even with dirty oil. I wish I could lockwire those screws since they always seem to loosen up with flight hours.
4) This is the new puck that gets inserted after the old puck is pulled out. Spring washers and slots provide variable flow in both directions.
5) This is the old puck. The four holes with round metal balls block the flow in compression. That gives the solid ride as it is almost a full hydraulic lock except for that small center hole. In extension, all ports open. There is no proportional control or variable damping apparently.
6) The red nylon anti-scuff bearings were in great condition. They absorb chips and dirt and it is hard to see how they would ever need replacing. Mine just went back in as-is. There are 4 pieces, hard as rock.
7) This is the culprit. This bottom o-ring (2.25 OD, 2.00 ID, 1/8 inch butyl, black) was deformed and leaked like a sieve as pressure was reduced in the strut. This is the only o-ring under differential pressure in the strut and it showed by squaring the bottom face and losing its sealing capacity. Based on both my o-rings being deformed I would suggest they get replaced on a time basis. If you have leaks, start here. They are cheap on Amazon (100 for $10). The scraper seal, the only one we see when assembled was actually in great shape and I didn't touch it. These debongers use 5606 red hydraulic fluid. After assembling and pressurizing, taxiing and landing I had no leaks evident.