My .32 Hand Ejector 5th model is single action. Is it supposed to be? were some double action?
AFAIK all standard-production .32 Hand Ejectors were double-action. If yours only functions as single-action only (SAO), it has either been specially modified to work that way, or it's broken.
Purposefully rendering a S&W revolver SAO can involve modifying the hammer, trigger, or both. Restoring the double-action function can be done by replacing the affected part(s), but it's not always a "drop-in" project; sometimes this works, but sometimes it doesn't, in which case a qualified gunsmith's attention may be required to make everything fit properly.
Also, you are likely to have trouble finding the appropriate parts. The names "5th Change", "3rd Change", etc. were not factory designations; they were endowed by collectors to differentiate changes in the internal mechanism. IOW certain internal parts are different with each "Change", and I'm nowhere near knowledgeable enough about early .32HE's to know if a newer (and presumably more commonplace) hammer and/or trigger will work in a 5th Change.