creating multilingual documents

Dear Uber TeXnicians :-)
Happy New Year  !
നവ വത്സര ആശംസകള്‍!
नये साल की हार्दिक शुभकामनायें ॥
あけましておめでとうございます

I am interested in typesetting multilingual (scholarly) documents using
XeTeX. However, I am a complete newbie as far as Tex/XeTeX goes. Anyway, in
order to be able to do the above, I would assume that I should be able to
input foreign characters into the document. For this I should have polytonic
keyboard? I am running Ubuntu Lucid. I have keyboard layouts such as "India
Malayalam" for inputting malayalam and "India Bholnagari". I have made few
test (multilingual) documents using XeTeX as the engine. But I am
dissatisfied with the way these have come out: for example, I do NOT have
കൂട്ടക്ഷരം or say , combination of letters(s+h+w+a=shwa, R+Y+E=ryee -->
ദീര്‍ഘം like "ശ്വ" OR "ര്യേ" OR "മ്മ" etc .
*Questions*:
# Is it possible to get different layouts?
# How do I make these shown above? I want to be able to input these
directly, rather than transliteration (manglish). Other method is probably
to remember the unicode characters and enter them in the document? Is it
possible to define our own keyboard layout, in some sense way that would
make it easier for people like me who are native മലയാളം speakers?

Sorry if the questions are not clear/too basic for all the learned folks
here on the list. I hope I am clear. Any advice/pointers much appreciated.

Thanks for your time and have a great year ahead.

Sincerely,
~rk

-- 
We want to know in order to make ourselves free. That is our life: one
universal cry for freedom. - Swami Vivekananda
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