Your post is very puzzling to me, since you seem to have some chemistry knowledge yet seem to lack common sense; although that's not to say that one implies the other. The answer to your question is yes, it is easily done, but my question for you is "why?"
First and foremost, this is far from novel and perhaps you should do some more searching around before posting.
In addition, why in the world would you extract 5-HTP from seeds when it's already available in almost pure form from about any health food store; even if you live in a third-world country obviously you have internet access and that should be enough..
That being said, 5-HT doesn't cross the blood-brain barrier, so let's just say the delivery route would involve a needle overcoming this little road block for you. Of course, serotonin has no need to do such a thing on it's own, since the reaction you are referring to already takes place inside your brain.. so why the burning desire to perform it externally "in a flask?" (why you put so much emphasis on this is beyond me.)
Besides, simply raising serotonin levels in your brain would be far from a psychedelic experience.. why do you think SSRI's are not all that fun? Hallucinogen's work by *selectively* activating *certain* 5-HT receptors in the brain. FYI, there are also receptors on serotonin-releasing neurons which are called "autoreceptors" or "presynaptic receptors", which are activated by serotonin itself, and thus, when agonized, will actually decrease serotonergic transmission in the brain. They act primarily as a feedback mechanism for maintaining the homeostasis of transmitter levels. You see? Your brain is smarter than you think!
Well, maybe...
My suggestion if you want a little 'psychedelic essence,' is the following; once you figure out your synthesis of serotonin, do some more research and devise a synthesis, "in a flask" of course, that adds two little carbon atoms onto that nitrogen (the one at the end of the aliphatic chain of course!) After that, inject a grams worth into your arm, I promise it won't even irritate your skin!