Jamma Board Question

[dieseldogpi]

New to all of this arcade stuff and I have a question.  Bought a complete setup for Golden Tee Fore.  Includes all the wiring, pcb, hard drive, power supply, etc.  After I purchased it from the dude, he sent me an e-mail saying:

"please check and re-check before powering up.
keep hand on power switch till you know there is no smoke.
once you let the smoke out of a chip it`s no good."

What is he talking about?  I am new to this so excuse my noobiness.  Before I do anything I want to have a good understanding of what I'm dealing with.  I was hoping to get it all hooked up tonight so I can test the monitor I got for free to troubleshoot.  Any info would be appreciated. 

[Ginsu Victim]

He's talking about the magic smoke that makes games work. If you let it out, it won't work.