Oxford bilingual gives,
opinion a (evaluation, judgment) opinión f; professional/expert opinion opinión profesional/de un experto;
I’d like a second opinion
me gustaría consultarlo con otro especialista
Would you understand the same in Spanish if you'd say something like
me gustaría tener una segunda opinión...?
I would understand it also, if I'd say,
me gustaría tener una opinión adicional.
Well, can somebody give me a second non opinionated opinion about my personal opinion?