You should check and adjust the bias anytime you make repairs or replace components. That is the correct thing to do and it is very simple to do. Since you changed the output transistors yourself, you already know where he output emitter resistors are. Place a voltmeter across one of the output emitter resistors (with the unit off and unplugged, with the dial on voltage, plug the unit in, turn it on and measure the output voltage in millivolts. Ask the manufacturer what the bias current or voltage should be through or across the output emitter resistor. If they give the bias in current, then you want to check the voltage = IR, where I is the current value they give you times the resistor value. If they give the value in millivolts, then simply read the voltage. The bias potentiometer should be adjusted after the device has sufficiently warmed up.
The output transistors are biased for a reason, to not check and rebias is a mistake.