I am sad

Let's play guess the amplifier.  Is it bigger than a bread box?

Is it a namebrand most people know?

Does it have a meter on the front?

Is it pretty to look at?

Let's play Read The Thread.

The name of the amp has been said 3 times already.

The first step with any problem is contacting the dealer who sold you your unit.  The distributor or manufacturer is much more likely to respond quickly to a dealer complaint.  The next step up the chain is the distributor.  If this is not something bought through a dealer you a sort of stuck doing as you have--communicating with the company. 

From your sketchy description of the situation, you somehow got a diagnosis of the problem and are expecting the company to send you the parts to fix the amp.  Who made the diagnosis and who is going to do the parts replacement?  If it is someone other than yourself, you might get that person to help with the company.  Most companies do not want just anyone mucking around in their gear and will want some assurance that the repair will be done correctly and safely.  A bad repair could mean more than just the gear not working, it could be unsafe and it could expose the company to liability.  It is not your fault that the company has stopped communicating, but, perhaps you might have to re-think your plan to do the repair without sending the amp back to the manufacturer.

I had a pair of speakers that were sensitive to source, the kef R105/3 with kube. I finally found an amp krell kav300il integrated that smoothed the rough edges in the upper mids/treble. Even with a 2nd power amp driving the woofers the krell would overheat and require service. Once the warranty ran out, the model was discontinued and the unit failed again I went back to trying different amps, but I ended up building an entire new system because I couldn't get the synergy back.

Most companies outsource the different parts in their products so you might be able to go around the amp brand and locate the manufacturer of the $300. part, might even end up only costing $150. 

In your communications with the company, did they agree to sell you the module and then not follow up with any further communication?  I am a bit confused as to how the problem was diagnosed and why the company would agree to send you the parts to do your own fixing.  That is quite unusual.  Most companies don't want the customer so much as opening the equipment case and have warnings about voiding any warranty if the case is opened.  

I am also a bit confused about your switching the two modules to see if that would effect a cure.  Do the two modules have identical parts numbers?  Did the amp only fail in one channel such that a swap of modules in separate channels could confirm that the failed module was the cause?  Did the company recommend this as a diagnostic step?  Did you confirm that it was safe to do the swap?  If you did this on your own, did you practice proper grounding of yourself to prevent electrostatic discharge damage?  It is not clear the extent to which the company endorsed your plan to replace the module and then failed to follow through.