US to Euro product code

[conker]

Hey guys.
I have a US N95 (0548763).It originally had the greek language but after I updated the software with NSU I lost it.
I visited a Nokia store and they told me that it happened because my phone is from the US and there's nothing they can do.
I'm about to change my product code to a european code to get the greek language back.
My question is:

-Will changing the product code from US to European lock my phone?

It's not a branded phone(Vodaphone etc.) I bought the phone without any sim card and it works with my old sim card.As a matter of fact I swap between 2 telephony providers(2 sim cards) without any problem.

Any help would be appriciated.Thank you in advance.