a. Nope. There is a native module. But I would recommend to use the DBI. You get a more general knowledge it becomes easier to convert to a different database

b. This I don't know... *Looking down on the floor in shame*

c. No it is not the only choice, but here you can find the info http://www.symbolstone.org/technology/perl/DBI/index.html

Note: It is PostgreSQL you can find it on http://www.postgresql.org/ ;)