HELP! Urgent help need regarding Macbook Pro 2009

Hey everyone.

Today my Macbook Pro 15,4" from 2009 suddenly stopped working :(

It froze and then for three hours it refused to turn on.

When it then did turn on it was just a grey screen.

An hour later I finally made onto the login, where it then froze

I then tried turning it on and went into Disk recovery but it froze there again.

I then deleted the Hard drive in disk tools BEFORE it froze again. When I turned it on and tried reinstalling from USB it froze (tried three times)

I then opened up the computer and removed the RAM and SSD. I replaced the SSD with my old HDD and re-inserted the RAM.

But there is still nothing.. just a grey screen that flinches every now and then :'(

I'm in the middle of writing my Bachelors degree so I really, really need it to work.

Anyone have any bright ideas at to what I could do?

All help is really appreciated!