I have a 1997nissan altama and it over heats bad is it for sure a blown head gasket

Try the radiator cap. If its seals are bad can cause overheating even pegging the red..

And if there is water in the oil yes you have a bad head gasket

If it is blowing white smoke out the exhaust or if it has oil in the coolant or coolant in the oil then yes your head gasket is gone. A cracked head is also a possibility if you have overheated the car badly.

Aluminum heads, getting hot, chances are they are warped now, causing head gasket to leak...

My Nissan Altima was also overheating to the boiling point couldn't find the problem till a mechanic told me to tighten the serpentine belt and that fixed it it was tight but was slipping at higher spreds