if some electrical repair shop cant fix it..
that means the circuit board isnt compatible with the new pieces of today.
probably means the circuit traces are too high of a resistance.
and that means,
you could keep the outside casing and all of the menus.. but you would need a new circuit board built custom.
custom work like that .. could be costly / might be utterly boring with the surround sound going on.
when the technology moves forward.. the repairs wont be compatible with the older electronics.
IF / when ... the repaired result wont be anything the same as a whole.
things like super bright signal to noise ratio .. that might still exist.
things like better slew rate .. that might still exist.
some chance of the result sounding colored.
sounding warm mixed with a lower harmonic distortion.. you could run it new for a while, and if it oscillates a year or two down the road.. it could be a fire hazard.
or it might break something else connected to the amp.
too many reasons to simply do the job and hand the product over.
you need to be involved with the project to ensure safety?
electronic repair persons meet a standard and forget about it.. it keeps their insurance at a 'no need' basis.
maybe you can find an electronics repair shop that is willing to have you bring the repair back in some time to get a checkup and replace some hazard parts that are close to failing.
it keeps the electronics working, and it puts more money in the electronic repair persons pocket.
but be warned..
sometimes you will start replacing things and 'one by one' the hardware gets transformed into something completely different.
so each time you hand the repair back to the customer.. the new sound might be terrible and the customer doesnt like it.
maybe they dont want to pay for it.. or maybe they are confused about why it sounds different.
relevent towards the hardware design and actual parts used inside the design.
because life is made of many flavors .. you might have asked an electronics repair shop that was confused (or lazy)
it may very well be one of the flavors that is better to leave it alone than go messing with it.
maybe you know something the electronics repair people dont know (usually slew rate)