Multiple issues... Running HOT, White Exhaust, & no heat

So, to begin with... I think I may have tried to haul something too heavy last weekend. That being said, today (five days later), my 1989 b2600i started puffing out a lot of white smoke/exhaust while I was sitting idle at a traffic light and then when I opened the hood to check the oil level, it looked as if oil or some sort of fluid had been sputtering about. After letting it sit for a while, I checked the oil level and it was fine. I was driving it home and noticed that the temperature gauge was peaking out in the hot zone so I pulled over and noticed steam coming out from under the hood. When I opened the hood it sounded like my radiator fluid was boiling over and was spewing out the overflow tube. I also noticed that my heater inside my truck stopped blowing hot air as well which is no fun in the cold weather. Then again, either is walking, so what do I need to do next? Head gasket? Replace radiator fluid? Check something?

Thanks in advance. As I've posted before, I'm not a mechanic but I'm learning so be as clear as possible in your explaination. I have a repair manual but I always appreciate real people's responses.

Sounds like you've blown a head gasket and overheated it. White smoke in the exhaust is an indication of coolant going through your engine. You're probably going to want to pull the head and have it checked for warping and cracks as it's prone to both. I would probably be inclined to buy a new aftermarket one that is beefier in all the right places and install that versus rebuilding and or machining an OEM head. But first thing is to probably get it pulled and inspect the head gasket.

When you put it all back together, you'll want to make sure that everything in the cooling system is 100%. You don't want to risk overheating again. Think water pump, thermostat, inspect radiator, hoses, ect.

If they haven't been changed in 10 years, the now is a good time to replace the hoses... there are several small ones starting at the thermostat and they work there way around the back of the engine and included the heater hoses. Most are custom molded - so I would go with OEM Mazda parts. They'll cost a touch more - but not too much.