Your "radio shop" should be able to load a working S-record using "shop tools" that MAY get the radio working again. It will still need a full alignment after this is done.
There is no "firmware/flashing" to be done on an MT2000. The MT2000 has firmware on a masked ROM, and is not "flash upgradeable" like the MTS2000.
The problem is not firmware related at all, it is a CODEPLUG problem that can be fixed provided a good CODEPLUG is loaded into the radio's EEPROM, provided no hardware failure caused the CODEPLUG corruption.
One thing we are starting to see on 20 year old radios like this is the subject of "EEPROM wearout" which can cause FAIL 01/82s and other issues. All Motorola radios of this era (MT2000s, MTS2000, JT1000, Astro Saber, Astro Spectra, etc) rely on Atmel EEPROMs to store the codeplug (both internal and external) and the EEPROMS, like any solid state memory, do have a finite number of write cycles.
In these radios EVEN WHEN YOU ARE NOT PROGRAMMING THEM, background writing occurs to the EEPROM of things like last used channel, user programmable scan lists, MPL, etc, and on trunking radios things like CC lists, last affiliated zone/channels, etc. Over time the cells in the EEPROM chip itself literally wears out, when this happens and the radio's operating system can no longer use the EEPROM, you wind up with a FAIL code or weird problems.
The EEPROM chips are cheap and it's a simple fix, BUT it requires the ability to solder/desolder TSOP and BGA chips properly.
Just something to ponder when potentially spending real money on a 15-20 year old radio. While well made, these age related problems are just now starting to show up. And they require advanced surgery by trained persons to bring back.