there is parts of a Giss System rebuild
the first part is the disassembly of the gun so the guts can be removed, and i being a model 75 owner that can be a challenge and it is not the disassembly per say but the reassembly
and then you have to do the power plant
the Giss System rebuild is not hard but it is technical and whereas a springer you have a seal, 1 spring, and the R&R is straight forward
of course, tricks are needed in all of this but not to the level of the Giss gun
just getting the seals on is a pain but i wander
you can take the info for a model 75 and have what you need for any model 60 series rifle the guts are the same
it would be the trigger components that would be different and the 60 series rifles would have fewer to deal with
i have done many Diana model 6 pistols but i would never do a model 75
i did a FWB 90 with never doing one and i sweat bullets getting it done so many small pieces at the rear sledge to deal with
file:///C:/Users/user/Downloads/Diana_Walther%2075-2.pdf and there is the clean up in the tube the seal will have turned in to a soft crumbly epoxy, wax material and the piston has smashed it in the bottom of the tube and is your job to clean it all out, in your case you would take the barrel off and fine a cylinder and fill till the tube was completely surround by, i use rubbing alcohol and then you soak and scrape and soak and scrape i use a dowel with a slot cut in the center
and you clean and clean and when you think you have it clean do it again i always run a brass cup brush down the tube with a cable Dremel tool at the end and clean one last time i coat the tube with ULTIMOX 226 just a haze and now you can start the rebuild
so, you see i got off track but you also see it is a lot of work and the reason you do it slow and correctly is because you don't want to have to go back in and do it again, in once and out and finish
just some observation from an old man maybe something will be learned