Advice on OSX cocoa app with Python backend

[Socheat Sou]

After a brief, but informative, discussion on Freenode's  #zope
chatroom, I was advised to consult the gurus on c.l.p.

I'm working for a small company who is in desperate need to rewrite it's
15+ year old, flat-file, client-tracking database.  The staff uses OSX,
while I administer the couple linux servers we have to run our website
and some internal sites.  In our initial brainstorming session, we
decided to go with a Python backend server, handling the database and
business logic, and a native Cocoa application on the client side, with
enough glue to make the two stick.

Also, after a bit of research, I discovered Twisted and PB.  I figured
I'd have to write a customized backend to meet our needs.  However,
seeing as how 1) I've never written a netwo
rk application before, let alone a multi-threaded application and 2) I'm
the sole developer
 on this project, I was looking for as many API's, modules, frameworks,
and/or prebuilt solutions as possible to help me out.

I initially thought of Zope because I had often heard it referred to as
an application serv
er, so I thought it might be something I could use as a basis, write the
business logic, and have the Cocoa application, with some PyObjC,
communicate with the Zope server.  We're definately not looking for a
web-based application, so I wasn't quite sure Zope was what I wa
nted.

For those that are interested, we're looking at using MySQL as the DBMS.
>From what little I know of OODBMS it doesn't seem like the right choice
because aside from data entry and client record lookups, the biggest use
of the database would be to generate reports and tabulated data on an
arbitrary set of fields.  I've read that this isn't exactly the strength
of OODBMS?

We are also looking at a server-client architecture, rather than
individual clients connecting to the database over the network, because
there are some features the staff would like (such as something similar
to message passing between each other, and also being able to administer
connected users).

Does anyone here have any experience building an OSX application with
Python running the show behind the scenes?  I hope I didn't come off as
asking "tell me what to do", but rather I would appreciate any advice or
links to resources that might be helpful in this project.

Thanks for your time!
Socheat