replace radio for 1990 Mazda Rx7

I am brand new to this site and very untechie.  My husband has a 1990 Rx7.  The radio/speaker system is acting up and he wants to replace it.  We went to a general audio place and the guy who looked at  it said he was very familiar with Rx7s.  He said they best they could do would result in fewer speakers and he thought we should try our dealer.  (This was 2 weeks ago - yesterday I found out that guy is no longer with the company.) 

Then we talked to our service rep at Mazda. He says parts are no longer available.  He said we would  have to go back to the after-market people.

Does any one have any suggestions? I know I haven't said exactly what is wrong - that's because I hardly even ride in the car!  My husband is so depressed about it, he doesn't even want to spend the time thinking about it.  If anyone thinks they might have any suggestions, I will try to get him to give more information.

The best possible answer would be the name of someone in the Pasadena California area who could/would be able to help get the parts and fix it!

I don't know if you are still interested on info for the RX7. I have the convertible and I found out a few things as I just replaced my stereo and door speakers.

Apparently the RX7 has amplifiers mounted throughout the car, more so if you have a convertible. It appears the rear speakers have amplifiers right on the back of the speaker, the door speaker amps are somewhere in the car and there is another amp for the headrests (Covert. Only). The important question is, do you have an electric antenna? This matters as the relay for the antenna also supplies part of the power path for the amplifiers, so it needs to be hooked up. I found this out the hard way... I installed an Aiwa deck, for the front Aux input and two Polk Audio DB650 for my doors. I had to drill extra holes for the door speakers, but other than that, it was fairly straight forward. I ordered all the parts from Crutchfield, including wiring adapters, which saved the stock wiring harness from being hacked or spliced. I did leave the headrest speakers and the rear speakers in place, so if you want to replace the rear speakerst, you will probably need an amp to drive them. For me, It all worked nice and sounds great.