Land Rover Repair: Engine Died Completely?, range rover classic, engine coolant

Question
Several months ago, I had an oil change on my '89 Range Rover Classic.  The technician put in 5W30 oil, which I thought was odd, but the car ran ok. About a month or so later, the car simply stopped running on my way home.  The engine coolant gauge had stopped working a few months prior, and may be a red herring.  The battery was fully charged.  I wasn't able to get it to my regular mechanic for a month and a half.  They changed an ignition coil and said it was ready.  I picked it up, but the engine made a loud chugging sound (they said it made that sound after I had it towed there, they finally got the dead battery charged, and they managed to start it before the new coil).  I had no power at all on hills, so I took it back.  They are telling me something went wrong at the last oil change, and the engine was damaged.  Does this sound like the car is totally dead? Can you think of anything simple they haven't thought of?  They have put $200 of work into it just investigating now, and it will cost more to have them check the engine "canon lifts."  I am not blaming the oil change technician.  The car is old, leaks, etc.  I need to know if it is time to say goodbye, but I am still paying for about $3,000 of cumulative bills for repair over the last couple of years.

Answer
The use of 5-30 oil should not precipitate a failure in an old Rover.  We use Mobil 1 5-40 oil in old Rovers here at Robison Service.  I think there must be more to this story.  I have no idea what's wrong - I can't see your truck from here - but what you face is always the difficult choice on older trucks.  Diagnosis costs money. Do you proceed, or just quit.

I will say this.  There is no such thing as "cannon lifts" in a Rover.  Are you sure the shop who has the truck is truly qualified to do the necessary diagnostics?