Our disco 2 stopped working well when my Mrs was driving it. She got recovered to a garage. They are saying it runs with lots of smoke on the start up. They think there is diesel in the dip stick. They suspect a cracked head. They are saying 2k for a specialist to get a new head and fit the bits. At least 600 for their labour. Which is maybe more than the value of the car. They don't know what else. they will find. Do those costs sound reasonable?

You can get a recon engine supplied and fitted for a lot less.
You can get a TD5 as-is for a lot less than that even

Yes I think an engine swop sound the best then keep your unit if it not a part of the deal and work on it your self