307 diesel Back Pressure?

I lost my oil plug and my dip stick was sticking out more than it should. I

went to a Garage repair station to ask for ideas or a diagnosis, all I got

was " Your Engine is F-c*xD! it's back pressure and it's F-c*xD!
36 hours later my head is also in the same state. I was not given any idea

on how to rectify the problems with my car, only a sly smirk, off some 
greasy dip **** who was looking at me like I was some money machine.
The car is running OK but it seems be going through more fuel than normal.

Any Help please would be appreciated.

                  Thanks in Advance                 Tom