Hi, desert--
Add my voice to the list of those who (1) want you to feel better! and (2) have been where you are.
You mentioned wanting a brain transplant. Believe it or not, therapy and meds can provide that.... it is amazing.
One of the most insidious things about depression is that it makes everything look terrible. So therapy looks terrible, meds look terrible, going for a walk looks terrible, everything that might help looks terrible. The other insidious thing about it, at least for me, is that it makes it hard to move, kind of like walking through sludge. With a friend's help, I got myself through the sludge, sat in my doctor's office (just my regular general pratitioner) and told him I felt like my brain was made of dark clouds. He wrote me a prescription, I went to the pharmacist, and by THAT AFTERNOON the clouds had started to clear up. I have told this before here, but it just seems worthy of repeating

By a couple of days later, for the first time in my life, there were no clouds. I had fantasies about putting the meds in the water supply (don't worry, I didn't)-- just the thought that people could be helped as I was and not know it filled me with empathy.
All of which is to say: the clouds are not you. You did not make them and are not less of a person because you have them. And you can be without them. The hopelessness you feel has nothing to do with reality, and everything to do with those dumb clouds. They are dishonest and confusing and they do not tell you anything true. Blow them away with a big giant fan.
As for therapy, I agree with everyone here that it is just a lifesaver. It is difficult to explain why. It has something to do with a combination of finally admitting that you are going to focus on yourself, and finding someone really helpful to provide support (when many of us never had that in our childhoods and secretly crave it). Just the hopefulness that therapy infuses me with is worth every minute of it-- this sense of "we are going to make this better! And maybe even totally fix it!" Wow. That is powerful.
And, for me (and maybe for you?) therapy was great because secretly I thought I was quite seriously flawed. When my therapists laughed at that statement, it was really helpful to see. My only flaw was thinking I was flawed, to paraphrase brother Longtire's quote.
Please keep posting. This is a very intelligent and articulate group that happens to consist of folks who have been where you are.
{{{{desert rain}}}}