It appears that you are trying to do mechanical things prior to obtaining mechanical abilities. If there is a washer with tabs that are bent into the spanner wrench slots, it should be very obvious that they must be straightened before the nut can be removed. One would hope that if a tab is necessary to hold the nut in place, the nut should come out pretty easily. Spend a few bucks on the proper spanner wrench to remove the nut. A pipe wrench might work, but it might not. There usually isn't much material to grab on to on the smaller cylinders. Now, once you get the thing apart, do you have something to hold the rod so you can remove the piston retaining nut? A vice and an impact wrench usually makes easy work of it. I just rebuilt a loader lift cylinder last week. The hardest part of the job was installing the new inside seals on the packing gland followed closely by getting the seals on the outside of the piston. It took me several attempts and the better part of an hour because of my weak arthritic hands. I had to devise and conquer, so to speak. Be prepared to heat the new piston seals in hydraulic oil for awhile to get them pliable enough to work with. You will need something like a vise to hold the piston well enough so both of your hands are free to work the seal on to the piston. Watch the orientation on all of the seals. Also, watch some Youtube videos as there are some tricks of the trade that come in very handy. You may be time and money ahead to just take the rod assembly and the rebuild kit to a hydraulic shop and pay them to install the seals. Good luck.
