Oh man, I feel your pain! That 3am PLC crash with a discontinued S7-300 is every plant manager's nightmare. Here's your emergency playbook:

1. **Immediate Triage**: First, check if you have a backup of the PLC program. If not, try to access the CPU memory card - sometimes the program is stored there. Check for any diagnostic LEDs that might indicate a specific module failure rather than the whole PLC.

2. **Emergency Repair Services**: Contact specialized PLC repair companies like Sona Controls or Longi Electromechanical - they offer component-level repairs for S7-300s and can often fix issues that would otherwise require replacement. Many offer rapid turnaround and even on-site emergency services.

3. **Used/Refurbished Market**: Check industrial automation suppliers who specialize in legacy equipment. Companies like Amikong stock, test, and repair S7-300 CPUs and modules with multi-year warranties. This can get you running in days instead of weeks.

4. **Temporary Workaround**: If it's just one module, can you bypass that function temporarily? Sometimes you can use manual overrides or temporary hardwired controls to keep production limping along while you source parts.

5. **Long-term Strategy**: Once you're back up, this is your wake-up call! Start planning migration to S7-1500 or another modern platform. TIA Portal can import STEP 7 Classic projects, but budget for manual rework of complex logic. Siemens has announced S7-300 phase-out starting October 2025, so you're not alone in this boat.

The key is having multiple backup options - repair services, used parts suppliers, and a migration plan. Don't panic - there are still solutions for these legacy systems!