I wouldnt say its rocket science, but takes some common sense and a selection of tools along with a good vice. The jack pictured is either a Late Walker, or Early Lincoln jack and its hard to tell by the picture but looks to be 4 ton but you first need to identify the modle number. There should be a plate at the base of the handle where it mounts to the frame. My biggest concern looking that jack is the condition, It looks rusty and if the frame is rusty i would be concerned about the actuall pumps and ram, Not to mention the time its gonna take to break that baby down. If your wanting to rebuild it, Get it up on a table. I use a rollaround cart where i can get on both sides, Start on one side and remove all the nuts on the cross pins, Front wheel and the big nut on the main lifting arm. Then disconect the U-joint where the release rod meets the actual unit itself, There should be a cotter pin or a small bolt (it will probably break), Disconnect the pump linkage. Essentially what your gonna do is take off 1 of the sides so you can get to the actual Unit, as you will notice that it ears on it that sit inside the frame. Probably wouldnt hurt to spray everything down with a Rust buster or something similar. You can spend upwards to a day sometimes getting rusted jacks apart trying not to damage them. Once you get to this point then i will go from there analyzing the condition of the pumps, ram and if you have the dreaded spanner tank nut.