If your car is as rusted as the rest of us in Canada, then replacing the gas tank can be a real can of worms. I replaced my gas tank shield (my original rusted out and was banging around). I ended up snapping the head off one of the bolts which also holds the tank,.... I had to drill and tap through the gas tank flange and frame to bolt it up. There is a lot more to be removed to do the entire tank and I can see one snapped bolt or clamp after another.
http://www.mazdas247.com/forum/showthread.php?123833387-How-to-Replace-Protege5-Fuel-Tank
http://www.mazdas247.com/forum/showthread.php?123718385-Has-Anyone-Had-Their-Fuel-Pump-Cover-Leak