I’m trying to learn about the spectral theory of automorphic forms (reading Iwaneic). I think I would benefit from a source for some of the more basic complex analysis/spectral theory to reference as I go. I’d like to see derivations of the analytic continuoation/functional equation of zeta and gamma functions specifically, and potentially some of the Fredholm theory and theory of differential operators. I guess a source on complex analysis as it is used in number theory would be great. THanks in advance.