I of course have no idea the actual procedures to follow in Colorado but it seems to me the following would be pretty much standard.

See your family doctor. He/she will do a quick assessment and if they feel it is required will make a referral to a professional who can make that diagnosis.

Note there is a difference between Psychologists and Psychiatrists. While both are able to offer you a diagnosis only the psychiatrist can prescribe medication. On the other hand, not a lot of psychiatrists can offer therapy. I am fortunate, mine does. Thus, many people see both (another option is that in some cases a psychologist will work with your family doctor in order to get you prescriptions).

The impact of a diagnosis? Frankly I was relieved. Finally there was an explanation for my whacky and difficult life. Finally too, instead of feeling I was alone, I felt a sense of belonging with the realisation there were others just like me out there. This is especially true as I attend support groups. I am fortunate that my boyfriend has lived with people who have been mentally ill in his past. He recognises the changes in my mood and has been a godsend in helping me when things get difficult. I expect that there would e a similar benefit when two people each with a similar mood disorder reside together. Sure there will be difficulties but an understanding I think would go a long way.