The source says three different players have been discussed as potential pieces for the deal. All three players played significant time with the Marlins last season. It is unlikely that all three would be involved in the deal.
The Marlins have been particularly vocal this offseason as they attempt to revamp their franchise for the 2012 MLB season. They have already extended offers to top free agents, including Albert Pujols (link), Jose Reyes (link), and Mark Buehrle (link).
Gio Gonzalez had a career year with the Marlins in 2011, pitching 202 innings of 3.12 ERA and 3.64 FIP ball, his second straight 200 IP, sub-3.50 ERA season. Gonzalez will only be 26 in the 2012 season and would likely cost the Marlins a hefty price in prospect because he will not become a free agent until 2016.
If the Fish want to acquire Gonzalez (and I would not be averse to this, since Gonzalez is very affordable and quite good), the team will have to pony up good talent in return. One of the chips would undoubtedly have to be Logan Morrison, as the A's would not be interested in an older player like Gaby Sanchez.