Hey UCD
When even trying to diagnose a problem it is often a good place to start at what has been changed as in majority of cases this is a good place to start ( not broke before changing anything but now is after changing something )
You are saying that the trans oil has been changed but you were not present when the oil was changed ( is this correct ?)
And
You had a problem with a coil ( did you test the car after you changed the coil) ?
The problem you are describing sounds like a converter lock up clutch staying locked up ( google how a converter works and you will see some vids on YouTube)
Basically a converter clutch will lock up at a certain rpm, I.e. 2500 rpm stall = lock up clutch will lock up at 2500 rpm
If your lock up is locked up from the get go then you will stall the engine either in reverse or drive.
If the engine is standard then the converter should lock up around 2000 rpm I think.
Not sure how you could test if it is the converter but I would imagine that if the engine was kept above the converter stall it should run. I.e if you took the car to 2000rpm and changed gear each time above 2000rpm or stall then it shouldn't stall in theory.
Now I have had Eff all to do with auto,s but that is what I have self learnt from the net and YouTube, reading books, not having a dig here but look at the net or ring a auto trans shop.
All the best mate, oh and before anyone else mentions
Stick a turbo on that De