Being a taxidermist myself, I am going to be upfront with you. Your idea is not going to work. You can't just embed a dead animal within resin and expect it not to rot. You have two options here: A.) Pickle the fish in a jar of alcohol or formeldahyde. Make sure you use a sharp needle and poke a few holes through the flesh to allow penetration of the preservative through through the skin. Also note that this is going to turn whatever brightly colored fish you once had into a sickly yellow brown bottle of dill cichlid. B.) If you want just the bones, I would look for a taxidermist in the area who works with dermistid beetles to clean skeletons and go from there. Also maybe contact a place I believe is called skull works that does dermistid beetle cleaning.
You could also take your specimen to a local taxidermist, and depending on the size of your fish it will be either conventionally mounted or freeze dried. You can also have a reproduction made of it. There are several world champion fish taxidermists who use replicas almost exclusively. I thought I would just chime in with my two cents
