W221 s class hk logic 7 amp

[Stew1984]

I have no sound or radio stations so I believe my amp has given up. Does anyone know the cheapest way out of this problem? I have spoke to a few companies to try and get it repaired to no avail. Also, does the replacement part need to be identical part number or is there a revised part number? My amp has the part numbers :a2218701789, a2218701889. Thanks