The "square-ended" trim cylinders are easier to get apart than the newer models that require a spanner wrench. You just need a crescent wrench or "plumbers" wrench and unscrew the end. Or use a pipe wrench and unscrew the cylinder from the internal end.
The replacement seals run about $15 per cylinder. The one "strange" bit is the piston seal (seals the piston to cylinder). Its a "compound" seal -- an o-ring underneath a Teflon band. The o-ring presses the band against the cylinder wall.
The guy on ebay has seal kits for the newer models -- charges a little $$ for the seals, and an outrageous amount for the "handling." If you can get the cylinders off, take them to a hydraulics shop and they can find seals that will work fine.
Craig