So between the 8 boards in an Omni 2 there are about 80 capacitors of the Tantalum variety -those known to fail suddenly either closed or open. An Omni with its original capacitors is prone to fail with voices stuck on or voices silent -either way the synth becomes unusable as an instrument.
Replacing a tantalum capacitor is straightforward enough -you remove the old one and replace it with a new one of the same capacitance and at least the same or higher maximum operating voltage and polarity while applying as little heat as possible to the board.
Those little blueberries are the capacitors you’ve read so much about. There is a trick or few to removing them. I probably took this picture to remind myself where the ribbon cables go.