Can anyone be a Calligraphist in a mosque, or does one need to be a
"holly man" ?
To clarify - if a secular Muslim wanted to take up this profession
would that be possible ?

Hello dogsbollocks-ga:

As far as I know you dont have to be a holy man to be a calligraphist.
And YES a secular muslim can take it as a profession.
I have everyday interaction with people from Muslim society and am
aware of the most of the details of the religion.

Thanks.

Hi leader-ga,

Thank you for this comment. Can I pay/rate this answer ?

Also - I am looking for someone with strong Islam knowledge,
preferably a Palestinian, to provide a paid editing service for my
book because it contains sections dealing with Palestinian culture. Do
you anyone who can help ?

Hi,
Anybody can become a calligrapher/calligraphist. However, in the
Islamic history a calligrapher is a highly respected person who
usually have a good position in the government. Some calligraphers
during the Othman empire used to have very close positions to the
king, as they are the only ones who know the secret of the King's
signature, government stamps and official seals such as Tugra (About
Tugra: http://www.aria.com.tr/touristinfo/about/turkey_arts_tugra.shtml)
Also, Muslim calligraphers are known to be very wise and knowledgeable
people in the religion, as they are the ones who write the verses of
the Quran and related literature. But again, it's not a requirement to
be a scholar in order to become a calligrapher.
I know a Palestinian Muslim who can help you in your book, he's an
Imam (Islamic teacher at a Masjid) and wrote several books about Islam
and history.
feel free to contact me if you are interested. 
Thanks