Well, you have the following options if you don't want to go to Amag for an original replacement:
1. Either you go to a junkyard and ask for the same head-unit in serviceable condition;
2. Or you buy an unviersal head unit (for 200-300 Euros you can get one with lots of features: DVD, GPS, PiP, rear camera ready, etc.) and a facia adapter
. Careful though if you decide to go for the universal HU, you may also need an adapter for the connectors!!!
Most of the HU come with these adapters, but you better make sure what kind of connector your car has (I'm 95% sure is an ISO connector) and if the HU comes with ISO connectors and/or adapters.
Talking about the work, it's not rocket science and on top of that youtube is full of tutorials.