Sorry I am not a diesel driver ( I hate them) , the only thing I could say is that a leaking valve cover can cause smoke, because the leak on the exhaust.
And I read someting about leaking oil lines from the turbo.

And about repair costs, you have to figure out I you want to spent 11k on your car, if you do you will have to drive for some time, because with a sale of your car you wint get your 11k back.