it wouldnt be anymore complicated than if you were just replacing the seals
the only difference is you are replacing the old gland (cap) with a new one

either way you would replace the seals in the same fashion

if you havnt repacked a cylinder before or if youre not comfortable replacing the seals without scratching the metal parts, then take it to the hydraulic place (sometimes repacking cylinders can be a little tricky, in general. this cylinder could be a piece of cake, but i dont know for this one in particular)

most cylinder seal kits only come with rubber parts and would be repacked the same way

DO NOT re-use the old seals if you do it yourself