it is a lot of work and you absolutely need to speak Spanish. There are some agencies which claim to arrange it for you - I had seen prices ranging from US$5,000 to US$9,000. I had also talked to a few local immig lawyers but honestly these guys did not really knew all that much. Given I speak fluent Spanish and lived in a few countries I just decided to do it all by myself. Message me for more - or you can reach me at my handle here at the swiss based proton.