[m-fine]

A regen only happens if it doesn't burn off on its own from extended driving, so there is no answer. You saw the light because it needed to regen and when it tried, you didn't give it enough time. The light warns you to take a nice long trip on the highway before it is too late. Nothing to worry about unless it starts happening frequently or the light doesn't go out after taking a long drive.

Also, I wouldn't replace a DPF unless you have to, and then only after trying to clean it first.