Hello all, this is my first post on this very helpful forum!

I am reading various threads here regarding the Nokia 5800.
I bought a UK phone which I am expecting it to arrive next week with the v31 firmware.

I have read some threads on how to debrand the phone and on how to hack it.
The hacking procedure involves downloading the firmware with navifirm, playing with it and flashing the phone afterwards.

Now the question is:
When I get the phone, the first thing is to install the Greek language by upgrading to a Balkans product code firmware.
If I do the hacking procedure (download the firmware I want and install in) will I have to change the product code as well?
Which is the best method on having a hacked firmware?

P.S. If I got this right, a hacked firmware means that apps do not have to be signed, right?

Thanks in advance.