if you must continue with this goofy project buy the bellows off ebay for $20-25. get a lens that fits the gx mount.
Operating GX lenses is problematic with the dead body. Mounting a view camera lens to the front standard would work well. I really like the idea of using the double cable release- it makes it easy to view up to the moment of exposure. If the GX is really dead (probably electronics) then this is just a fun DYI project which salvages what is otherwise only good for parts.
I do use a digital device in my photographic pursuits when necessary.
When someone rags on me for using film, I use a middle digit, upraised.