That depends on the circuit. What amp is it? It helps to know that, so maybe guys who have your amp will read this thread and put your mind at ease...
If it is a true auto bias circuit that adjusts each tube individually it wouldn't even matter if your power tubes were matched. Look at the BAT VK-75 or the Primaluna amps... those have auto bias circuits and do not need matched tubes. If it's just a simple cathode bias you'd want them matched, but you could still just pop them in yourself.
The only company I can recall that recommends sending an amp in for re-tube is Audio Research... but none of their amps are auto bias.
If it is a true auto bias circuit that adjusts each tube individually it wouldn't even matter if your power tubes were matched. Look at the BAT VK-75 or the Primaluna amps... those have auto bias circuits and do not need matched tubes. If it's just a simple cathode bias you'd want them matched, but you could still just pop them in yourself.
The only company I can recall that recommends sending an amp in for re-tube is Audio Research... but none of their amps are auto bias.