Mac MySQL conversion

I am a Macintosh developer who has built an OS X.3 application using a MySQL
database to store data. I am interested in porting it over to POSTGRESQL.
Can anyone give me a heads up on:

1. How different-similar the language is to run queries?

i.e. SELECT columnName FROM tableName WHERE columnName = someValue;

2. If there is an embedded version of POSTGRESQL for Mac OSX.3, so that it
can be installed in the same bundle with my app, and no passwords are needed
to run queries to it. Basically, a way for it to be completely invisible,
and run only when my app is running.

3. If I can run queries through the shell like I do with MySQL?

i.e. /usr/local/MySQL/bin/MySQL -u user -ppassword -D theDatabase -N -e
\"SELECT columnName FROM tableName WHERE columnName = someValue\""

Thanks for any input,

John