1990 Nissan Fairlady 300ZX Overheating

I have a 1990, 3l V6 Automatic, NA, 300zx that has done 150,000kms.

yesterday while driving home I noticed my temperature gague was about 3 needles below the hot line.
I pulled over and let the car cool down.
With the car running we added water to the radiator and I managed to drive it almost to my grandparents.

I had to pull over on the way there and I pulled over on a hill, I noticed brown water leaking out I had alook under the car and could see water dripping out from the back of the engine.

I know it came from the radiator somehow as I just brought the car got an inspection check done and was told there was little or no antifreeze in the radiator hence how I was able to tell the rusty water on the ground was from the radiator.


I suspect maybe a hose is cracked?
I have no idea and badly need help!
Do I have to replace my radiator because of it not having antifreeze?
Why would my car be overheating?
Also the radiator fan does not go when the car is switched to acc or the click before the car turns on. I have been told this is not normal.
I would like to know is this normal on a 300zx?

And could I have blown or cracked a head gasket?

How much would this cost? I have only had the car 3 days!

Thanks in advance for any help or advice!