Depends on the gearbox fitted!
The gearbox fitted to my 4/4 (1972), the filler is on the left, ie the passenger side if it's a right hand drive car. But I suspect from the year, your box is a different type.
However, the metal gearbox cover has a hole in it, to align with the filler and the vinyl/leather cover that goes over the metal can be freed from the mounting press studs, rolled up and gearbox filled. I'd be pretty sure that Morgan carried on doing this so roll up the sides of the cover and have a look.
No extraction pump should be needed, both mine and the later gearboxes have a drain plug at the bottom of the gearbox. Does take a while to empty out, I generally position my catch tray remove both filler and drain, leave to drain and go and have a cup of tea!
As original, it's a 12000 mile replace oil and check level at 6000. Original recommendation was for EP90 or 80 but I suggest not using EP90 as the thicker oil can cause problems in gearchanging until it has warmed up. EP80 hasn't given me any problems.
