re-assembling pcb questions

From the beginning:
- One trackspot stopped working and someone else has put it apart over a year ago.
- The trackspot had a burnt voltage selector switch which I recently bypassed.
- When testing the only thing that worked was the mic. No lamp or motors. Voltage is OK. No fuses were blown (not even when the vss ?).
- After more measuring and testing I found out that the circuit on the PCB, from the 24VAC connector (next to the fan connector) to the rectifier, has melted. Best way to fix this I think, is to solder a wire at the bottom of the PCB connecting them together.

My questions:
1. On the bottom of the 4 power transistors/thyristors/??? (REG1-REG2-SC1-SC2) is some white stuff. Is this thermal compound? And if so, is the standard thermal compound from a computer shop ok to use? Or is it OK if I just screw them down?
2. Since I didn't pull the unit apart, does it matter where the red and yellow-red transformer wires are connected? I guess not since it's AC.
3. Same question for the lamp holder connectors.
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