Flashing Folder, and Grey screen?

OK, so I've had my MacBook Pro for about 8 years now, always ran smooth until about a week ago I got this flashing folder and my OS wouldn't boot.

I looked it up on Google, mostly it pointed towards a failed hard drive I tried to get into the system recovery mode holding alt and ctrl R, and it worked like twice I was able to get to the options. But, they didn't respond when I clicked on them and the screen just ended up going gray.

I got to point where if i just let it boot normally, I got the flashing folder and if i tried to hold alt or anything it would show my cursor but just a gray screen.

I came to believe after what I read that maybe my hard drive failed, so I ordered a new one pretty much the same one I already had.

I just received it today and hooked it up properly everything seems to be plugged in right. When I went to start it with the new hard drive I just get a gray screen holding alt and ctrl R yield the same results just a gray screen!

Anything else I could try? Trying not to take it into the Apple Store and have to pay 600 dollars at that point I'd just buy a new system.