Denon AVR-X3400H front left output broken

Hello everyone, I have been the owner of the Denon AVR-X3400H for quite some time. For a while now I have noticed that the front left speaker no longer works, at first I was afraid that my speaker was broken, but now I have found out that it is the amplifier. So it only concerns the front left output, the cable and speakers are good. There is no warranty, does anyone have experience with this? Would it be easy to repair it myself or better to take it to a professional? I would like to hear your advice.