Flush or change my transmission fluid?

I have a rebuilt transmission in my 1989 jeep wagoneer. It's just hit the 3 year mark and in need of a fluid change. But I'm not sure if i should have the fluid flushed and changed a shop or do it my self. I figured since its just rebuilt that having it flushed wouldn't hurt it and probably keep the tranny running in the long run if i keep having it flushed. But not sure.

i would just change it.

Yeah I don't know if I'd do all that. Just change it and the filter.