Request for help setting up source tree

Hi,

I want to make an extension but don't understand the source setup well.
a) Do I need the full source of postgres locally?
b) Where must the source be? The project dir is ~/nbprojects/my_pg_ext
 and I am using the code of the fuzzystrmatch contrib as my "template"
from where to start
c) My installation of postgres is 9.1.6 and I don't intend to upgrade
for now. Can I use an extension compiled against 9.2.x code in my
9.1.6 installation?

I am using the Netbeans IDE but also understand Eclipse.

Thanks for any help/info.

RD