Answer:
Replace the motherboard.
Step-by-step explanation:
The motherboard is the core of the computer. If the motherboard is oozing brown stuff, signifying that one of the sectors has been eroded or is about to disrupt, it needs to be replaced before further damage can be made.
The screws in the hard drive can easily be replaced.
As for the memory sticks, they will operate best if they were the same brand and the same memory size and hertz.