[gnome-love] SW Developer want to contribute. How to start?

[Carsten Petersen <c petersen45 gmail com>]

I am a sw developer with app. 40 year professional experience. I'm just retired from my latest job. But I still want to do some sw. development. E.g. to contribute to the Gnome project.
But I have absolutely none experience in Gnome development! I would like to learn, eg. a new language Python.

Professional experience:
Languages: C, C++, C#, _javascript_, Oracle SQL.
Platforms: Embedded , Mini computers, DOS, MS Windows, Unix (client server systems).
Real time app., Web based app., Web services.
Different version control systems.

Other development:
Languages: Java, PHP, Mysql, a bit Ruby.
Platforms : Linux( Ubuntu), Web ( PHP based using Yii and CakePHP frameworks) .
Studied Test driven development.

But where do I start? Which programming environment do I need?
I know MS Visual Studio very well as a professional programmer.
At home I use both Eclipse and Netbeans ides.

Please give me some advices.
Can you propose a minor project, I can start with. And how to start.

Carsten