Scout Diesel DSG / Haldex problems

Hi, 

Thanks for allowing me to join, i've already cleaned some good info.

I have a small boat and i want to be able to launch on shingle / beaches as well as slipways.

I'm looking for a decent Diesel Scout with a DSG. My budget is 7K .

I've heard that it can be difficult to tell if the Haldex 4WD is working or not. I can't see a 

motor dealer or private seller being too happy if i ask to put it on rollers to check.

My first question is..  if the Haldex wasn't working, what is the cost to replace or recondition

the unit ? 

Second question, how reliable are the DSG gearboxes? 

Third question, what is the highest mileage i should consider buying ?

Finally is there anything else i should consider before buying. 

Any advice is really appreciated. Thanks