If anyone has any knowledge or advice on how much work is involved in replacing the heater core on 123 car. (82 240d)

I plan to replace my anti-freeze mixture today and before draining the system I thought I would add some "radiator flush" to clean system.

However, I would skip the flush at the advice of this forum.

My concern is that the flush would work "too good" and cause leaks in the heater core. (this happened to me with years ago with Taurus, which was a nightmare to replace)

Anybody, have any experience or general advice?

Thanks,
dave