Check with your Ag as suggested, but it would be worth contacting A&M as well. Compare services!
When you talk with them (both places!) ask about fees and services. If too high, then ask if it's possible if you do your own necropsy, can you send them photos and get a consult through email. Some do, some don't. You never know unless you ask - asking is free and it won't hurt.
https://tvmdl.tamu.edu/
I'm sorry that you are dealing with this and things are not going well. If you don't have any success with Ag or A&M, then still take photos and post them. We'll tag in folks to take a look and see if we can help you. A lot of us do our own, but that does not mean that we will know, but it's way for all us to learn and offer input.
I understand it's a difficult decision to make, so take your time thinking about it. Do offer your rooster supportive care while you consider all options. I would give him poultry vitamins a couple of times a week. Something like Poultry Cell that has E, B1, B2 and a variety is what I like best.
Since you hunt, I think you can handle this. Though not quite the same, you are still handling a carcass but just taking a closer look at the organs, intestines, etc.
If interested, here's a good necropsy manual. There's also some good videos on youtube, though quite long.
https://www.uspoultry.org/education.../Lesson11/PoultryAnatomyandPhysiologyPres.pdf