serious Overheating (?) killed my macbook...

I have a late 2008 macbook 13" that I had a problem or two with in the past. Aside from cracking the lcd, I started noticing the macbook getting extremely hot and would occasionally shutdown without notice/warning. The battery in it was run-down and the computer wouldn't run without being plugged in (I realize this may not be the 'healthiest' for my mac)...

So, I'm taking full blame for whatever problems I allowed to build up... but long story short, I woke up one morning to find that the macbook wouldn't power on at all. There are smoke/burn marks coming from the fan exhaust... and more worriesome: they casing around the keyboard is discolored as if it was exposed to extremely high temperatures (mostly in the center - around f;g;h;v;b keys.). When trying to start up the mac now, there is no more that a click/groan type noise accompanied by the led light on the magsafe cord dimming... there are no other signs of anything running; no fans, spinning sounds, etc.

What is the most probable cause and is there anyway I can diagnose the issue before taking it to get looked at?

Luckily, I received a iMac 27" before this happened... whether the problem is the logicboard, powersupply, motherboard; is there any way I can boot up the hdd of my macbook to access it on my iMac? I've read i can remove the harddrive and place inside an xhd case... but i was hoping I could skip this step and just connect computer-to-computer...

and questions u can answer would be of a great help. Thanks!