Things to check for "no sound":
1. Is the speaker connected (you say it is) and is it any good? Use a AA battery to confirm that you get a noise from the speaker. That also confirms that the wiring is ok.
2. Is the amplifier blown? Have a close look at the TDA1510 (bottom left corner, on the heatsink). Usually when they blow, you'll find a nice hole in the top of the chip. Sometimes it's only a crack, so look closely.
Yes, five flashes from the LED is good. It should be followed by some sounds from the DAC, the AY38910, and the TMS5200. What this tells you is that as far as the processor can see, the board is working, so the problem is on the output side of the sound board. If it's not a blown amp, it gets somewhat more complicated to figure out what's wrong.
There isn't a source for new parts. It looks to me like a Williams bushing may work for the flippers, mounted upside down, but you may have to modify it slightly. I haven't tried this. The bushings are usually ok. I have used Nylon washers in the past if the flipper sits too low to the playfield.
If the screws you're looking for are for the coil stop to the flipper mech bracket, those are M4 4mm pan head phillips. I don't recall the length off hand, but if you have a local hardware shop with a good selection of metric parts, you can figure out the length you need pretty easily.
The ramp lights trigger off the switch at the entrance. If they're not working, that switch is missing the ball going past. The scoring for the ramp triggers off the microswitch over on the left. There's a sound effect, too, that triggers off the entrance switch, but your sound board isn't working so you wouldn't have known that.