Hey,

now, when I'll receive the machine, I'll take off the complete LCD assembly and put it on my not working machine, if it works, it would mean that the problem is the original ribbon cable or the LCD I bought off ebay,
So I could buy a new ribbon (after having tested the LCD in the known working LCD assembly) or get a refund or a replacement for the one I already got.

If it still doesn't work, it would mean a problem in my motherboard because this LCD assembly is known as a working one...

If it works I'll recompose a phone with the least damaged parts and buy a new digitizer+film screen protector and maybe a new complete case...

Another thing that could be an idea is that I might buy a Neo900 motherboard (even though they are a bit pricey) in the future which I could put in the out of order N900.

I come back when I got the new phone