Codes on average probably take a maximum of 20 minutes to remove with the software.
They are probably messing you around. I dont even think you should need to leave the car with them at all.
I remove them myself in a few minutes assuming the problem has been fixed.
How much are they charging you anyhow just out of intrest.
Funny that the 02 bosch sensor is so expensive for such a small part.
You can generally give it a clean with some WD40 it may work as a cheap repair.
But u can replace it if you buy a new one, Can be a DIY if you know what your doing.
Check a mechanic if you dont.
If it is a clunking type sound. I once had a problem on one of the boxsters i had. I found the problem to be a loose arm in the roof bay.
Depends what type of sound really and how and when it happens. Seek a mechanic if its causing some driving problems.