I take it you've loosened the expander bolt on the stem a few turns and given it a sharp whack with a hammer? That usually gives it a hand. One of the guys at the shop said classic Coca Cola sometimes worked. I'd have to say that PlusGas worked on my '65 Speed.
As far as diagrams go, there is a limited one which explains what is contained within the front forks and can be found at www.moultoneers.info/tech-topics/classic-front
. I think Paul Grogan's 'The Classic Moulton' book has exploded diagrams. He says he's aiming for a reprint ready for the Bradford-on-Avon meet in September.