Thanks for your advice guys- I think what I'm going to do is just switch out all the monsters for 3rd ed ones of appropriate CR, and make the classed NPCS in ETools. I found a conversion online for the Memory Web (the thing that was giving me the most grief updating) so all is well!
I'm running this as a surprise for one of my players- about a year ago, we were talking about adventures in general, and he mentioned playing this one about ten years ago and said he'd really like to play it again. Didn't realise it was 1st ed, I only started playing about 3 years ago, so THACO and such things are all greek to me. My boyfriend has been very amused by my reading through the adventure and exclaming at various points 'AC 2!?? That's ****!!' Yes, he has explained to me how it worked back in pre-3rd Ed days
Ellie.