The 74ls245 is an octal buffer. To me it just looks like the chip was replaced and it was a lousy soldering job. Really lousy. With lots of rosin/flux left on the board. Get some 99% rubbing alcohol from the drugstore and use a q-tip to try to clean it up, front and back of the board. Then take a look at all the joints to make sure they're ok.
I don't know the ROTJ boards, and ROTJ in a SW cockpit would be weird anyway. So I'm guessing at the following. I suspect the "missing" chip on the daughter card shouldn't be there. That's just the way the board connects to the mother board. It's hard to tell from the overhead angle, but I think the screw would keep you from plugging in a chip even if you wanted to.
I assume you reseated all the harness connectors when you got the cabinet? Try removing the board and then powering up. Any response? Do you get a raster? Is the screen just a solid white? Solid black? Something interesting? Try turning up the brightness on the monitor to see it. Can you measure the power supplies...first with the board installed and then without? Do the cabinet lights work? (Marquee? Coins?) Stupid question - is it plugged in and turned on?
Actually I thought the monitor was off. But when I look again, the monitor seems bright (solid white) with some horizontal bands. Is it? If so then the raster is working. And the problem is limited to the board and power supply.