I think you have a wonderful attitude, welcome to this forum, I hope you enlighten yourself and find the right path.
My answers are not as cuddly as the others, I hope you do not take offence at any of them
Where can I buy fabric for tying a turban?
To me, this is the equivalent of someone wanting to join the army and asking where they can get a Generals uniform. A film I am currently watching, 300, for the 87th time, has this line in it 'earn these shields boys', a turban has to be earned, but many people make the mistake of thinking they can just put one on and it makes them a Sikh, in my view this sort of thinking should be avoided as it gives you false understanding and pride.
How does Amrit aid in a Sikh's spiritual growth?
it doesnt, the taking of Amrit has no magical or spiritual properties, it does not change who you are, or infuse you with anything. The taking of Amrit is a declaration that your head now belongs to the Guru. It is a statement, like 'will you marry me', those that take Amrit in the hope that it will make things better are deluded, in the same way that couples that get married in the hope it will save their relationship are deluded, We take Amrit when we are ready to give ourselves, body and soul, to the Creator.
-Can a non-baptised Sikh get married in a Gudwara?
It depends on the Gurdwara, and ironically what colour you are, if you are indian looking, then it is not a problem, if you are white, black, chinese, or anything other than indian looking, then someone will probably raise an objection, remember Gurdwaras are run by human beings, some of whom are more petty than others, does it have racist overtones, yes, it probably does, but the fact of the matter remains, two indian non baptised Sikhs getting married in a Gurdwara is quite common, two non baptised koreans would raise eyebrows and objections. Also, remember, getting married is not quite the same as the Anand Karaj, the Anand Karaj requires you to be at least aware what you are getting yourself into, and the spiritual responsibilities thereafter, it is a union between three, you, your partner, and Creator. It is a bit like ordering the most tasty dish on a menu, without any idea of whats in it, and then just staring at it for an hour, and then leaving. To most, Anand Karaj is just something to get out of the way before the drinking and dancing, to those for whom it is the best part, the most uplifting part, I have much respect, and admiration, and possibly even a bit of envy.
Is a baptised Sikh REQUIRED to be married in a Gudwara?
A baptised would not dream of being married anywhere else
Sikhs in America: how liberal/conservative are Gudwaras in the USA on social issues?
I find those that do not believe they are still living in India pre partition quite progressive, I am sure there are american members here that can guide you,.
Can Kara bracelets be any standard steal bracelet, or must it be a specially made "only for Kara use" bracelet?
I, personally do not consider myself Sikh enough to wear a kara, but that is my personal failing, having said that, I think the next time I meet my father, I may ask for one of his old ones, as I am getting better
. The best karas are those that are inscibed ' for kara use only' lol, no just kidding, I think the simpler and plainer the better, it is not an item of jewelry, or an item of show.
What are the sects of Sikhism?
Sikhism itself is quite simple, one Creator, love and compassion for fellow being, raise yourself to the best you can be, academically, in your mind, your thoughts, aspirations, physically, it is to be the best you can be, until you get to the point where you are Creation and Creation is you, and you see Creation in everything, at this point, Amrit Chak, and maintain this till you die.
There are other sects, some believe in a living Guru, some believe in Vedic practices, some believe in Martial practices, some follow other manuscripts, some are veggies, and some are plain on the make, the best advice I can give you is to read through some of the threads on this forum, they give an unbelievably unbiased view of most facets of Sikh life, educate yourself, ask questions, I hope you have a wonderful journey, !