Remove cylinder.
Get seal kit.
Remove outer snap ring.
Push cylinder guide back into the barrel about 1 inch to expose a snap ring groove on inside of the barrel.
In the seal kit find an orange ring that needs to be inserted into the groove in the barrel. The groove is contoured, so be sure to install ring proper way.
Then pull cylinder rod and guide from barrel. The orange ring allows second snap ring on guide to slip past the snap ring groove.
Then remove nut from rod, remove piston and guide from rod. replace seals and orings on guide and piston. and reassemble. The orange ring is not used for reassembly, it is used for disassembly only.