Land Rover Repair: Head Gaskets/Coolant Leak, combustion gasses, intake manifold gasket

Question
I first asked my mechanic about frequently low oil and coolant in my 2004 Discovery II SE in April '09 and he pressure tested the cooling system and everything checked out fine. At the same visit he replaced the intake manifold gasket and valve cover gaskets. I took the car back in August '09 and asked again about the low coolant and he seemed unconcerned. Unfortunately, I started refilling the coolant with Prestone and other brands since I was unaware I should be using a Land Rover specific coolant. Now, the car smells hot (like burning coolant/oil) and the check engine light comes on intermittently. I took the car to the dealer, and they told me my coolant is bad, the head gaskets are leaking oil, the front and back of the driver's side head gasket is leaking coolant, but there are no combustion gasses in the coolant. They recommend I replace the headgasket, the thermostat assembly (they say that's why the engine light is coming on), and reseal the transfer case. I've already spent over $1400 this year and the dealer wants $3700 to do the current repairs. When do I stop pouring money into this car and trade it in?

Answer
Your Rover may well need those things.  At Robison Service we receive overs from all over the East coast for work like that.  Does your truck need more or less?  There's no way to tell without seeing it.  Is the list real or a fantasy of a hungry service sales person?  There's no way to tell about that either but you do know there is a problem and the proposed work is a possible valid solution.  i can't say much more from here.