I finally finished Friends of ED book...
Very interesting, I even found informations I was not waiting for in a book : extend Flash Lite (via python, symbian C++) and packaging/distributing.
In fact, the only info I missing is "how to do you create and distribute content for several devices with differents screen size ?"
It seems Device Central could help it... I'll wait for the trial version to check that.
So, enought theory, let's go practice!! I'm waiting for my 5200 but for the first tries, I'll use the emulators (Flash, Nokia SDK, Sony Er. SDK)