can I change my heater core with my limited repair skills

This is a labor intensive job requiring the entire dash be removed down to the firewall to get to the core. With "limited" repair skills, this may be a daunting task for you.

I agree with Tireguy. To replace the heater core on most cars the air conditioning system needs to be evacuated, the dash usually requires major disassemble, not a simple repair. With times tight right now at least have the heater "bypassed" (joint the input and out put hoses together) because if you keep driving the car the heater core may burst causing possible engine overheating or burning you and your passenger.