Still learning

[flouese]

Still learning the idiosyncrasies of the 986 engine. I keep getting the following pesky CEL codes:
P410, P411 & P1411. I contacted my indy repair shop and they said they are O2 sensor related and not to worry.
A. Is this a true statement?
B. If it is, which sensors needs replacing?
C. If sensors require replacement, would buying (used ones i.e. from Woody) work?

I've searched the forum and see plenty of discussions of these codes, but not how to remedy them.

Please advise.