Late 2007 MacBook Pro 17" lost all sound and gets hot!!

So my late 2007 17" MacBook Pro has been acting up. Not only has it been slow but also...

1. It gets really hot! Fans running at 6000 rpm according to IStat Pro and fan control is not helping.

2. It crashes. Every time I try to edit video or do photoshop, the fans start blowing, it gets hot, freezes and crashes very quickly.

3. All my sound is gone. I get the Apple chime when I start it up, but my music and any video online gives me no sound.

4. Once in a while I get a distorted line across my screen.

Any ideas what could be my problem? I downloaded SMART Utility and it told me my hard drive is failing. So I'm in the midst of replacing it. However I doubt that will solve all my problems. Or will it?

I also discovered that one way to regain the sound I would just have to reset my PRAM, which I did and it didn't solve anything. Therefore I found that it could be that my logic board backup battery is dead? How do I know for sure?

Any other thoughts?