more than its worth. it would probably be better just to sell your 04 auto and buy one with a manual trans.
The 2013 Mazda MAZDA3 has a 5-speed manual.
The 2011 Mazda MAZDA3 has a 5-speed manual.
The 2009 Mazda MAZDA3 has a 5-speed manual.
The 2014 Mazda MAZDA3 has a 6-speed manual.
The 2008 Mazda MAZDA3 has a 5-speed manual.
The 2004 Mazda MAZDA3 has a 5-speed manual.
The 2007 Mazda MAZDA3 has a 5-speed manual.
The 2006 Mazda MAZDA3 has a 5-speed manual.
The 2010 Mazda MAZDA3 has a 5-speed manual.
The 2005 Mazda MAZDA3 has a 5-speed manual.
The 2012 Mazda MAZDA3 has a 5-speed manual.
This is a major mechanical project. Remove the clutch and manual transmission and the radiator. Install automatic transmission, new driveshaft, new radiator. You have just spent as much as a car is worth.