Sound startup: My baywatch does the same thing, "Baywatch will be right ba..." (instead of "back")
Lights: Yes, two lights good.
DMD: A very common problem on the small 16x132 displays (as used on five games, Checkpoint to Batman) is a failed R95 resistor. It is very common for this 33k, 1/2 watt resistor to go out of spec, or even open. This will cause the display to look garbled (see picture). Often the display itself is fine; it's just this resistor that needs to be replaced. <<Note this is from the pinrepair guide, it goes on and on with more possible solutions/issues with DMDs on these DE machines so you may want to find and read the whole thing>> Specifically on my DMD I had intermittent problems where it just went totally off after a while and once I reseated the connector on the power board the problem went away. Yours looks a little more involved.
Slingshot switch: There are two switches for that slingshot and they are wired together. If you want you can usually replace both switches at the same time and you can buy them already wired/soldered together and save yourself some time if you're not too handy with the soldering iron. You'll still have to do some soldering but not as much.
Nice first pin!
dedisp1.jpg