How big of a job is changing the heater core

What is your question?

It started to leak coolant on drivers side footwell and lots of steam out of all the vents. Temp gauge shot up to the limit. I was just1 block from my house so I limped it home. No damage to the engine I'm pretty sure.

What makes this problem better or worse?

I will not start the car in this condition

How long has your 1992 Mercedes-Benz 190E had this problem?

A week ago it happened