Hiding PG/SQL functions

Hi,

I have PG/SQL functions in Postgres database created using sequence of following statements:

(example)
CREATE OR REPLACE FUNCTION get_data RETURNS integer AS $$
...
$$ LANGUAGE plpgsql;

These PG/SQL functions can be viewed using pgAdmin. I don't like this because users can see the internal structure of
myprogram and they will try to cheat my program.  

My questions are:
1. How can you hide PG/SQL functions from other users, so that they can't see the functions, but they can still execute
them?

2. What do you think about this idea: Can you embed PG/SQL function in a C code, compile it to a shared library and
thenlet the users use it? How do you do that?  
This would protect my functions (I think).
I would rather not give up PG/SQL language as the procedures are almost ready. So embedding PG/SQL in C is feasible,
whilewriting all procedures from the scratch rather not. 

3. Where can I find more details about database security in this respect (ie. protection of my code). Even some links
tothe manual would be helpful. 

Thanks for the answers. I am just not kind of admin guy, I am kind of programmer guy.

Bigg