As you state capacitors partially electrolytic do degrade over time, a hum is normally the first sign that a cap is on the way out. Visually it may show signs of leakage or swelling.
I would look first at the power supply section, its likely a main power cap is at fault.
Other components can also degrade a little, like resistors, more so Power types, but its unlikely youll find many of those in a modern amp these days. Most solid state devices tend to last, unless shorted out or they over heating for any reason, if any blow its often due to a another faulty component down the line.
It seems your amp has two large 20,000uf electrolytic capacitors for the power supply, so I would say they need changing. Its well worth having it serviced. Good luck.
