Your unit is not an eMayWay. It is a SMEG+i.
The headunit's software cannot (of course not!) be replaced.
There is no satellite "part". Headunits in cars are not homecomputers where one can install applications.
I am writing the following words without any offense on my mind. I just think you're on the wrong track.
This is my true advise (the following is completely off-topic in a tech forum)
I am going to assume you are a private buyer, i.e. a consumer. I am also going to assume you never heard about the EU.
If you bought your car in the greek part of Cyprus (=EU) then your dealer has the obligation to fix it, if he promised the nav feature in the contract.
It is called EU-consumer rights- -> [Only registered and activated users can see links. ]
After reading the above link, read this: [Only registered and activated users can see links. ]