Firepower is an all time great, a true classic, and well worth the effort to get working...

... I say this as I agree it doesn't look like it's even booting in the pics you posted. Only the GI is on. None of the controlled playfield lamps are on, nor are the displays. This is a classic telltale of trouble with the boards. It could be and hopefully is a simple incidental issue, but is more likely the warning you should start reading up on troubleshooting Williams System 6. There are many common failure points and required steps to really make it reliable again. But it's worth the effort and the journey is half the fun...! Start with Vids Guide to System 3-7 here on pinside... I'm sure you'll get plenty of help as you go further in.

Good luck and welcome to the club. Oh and BTW even if it's not booting, that pf looks to be in great shape for an original