Done some searching around and find no recent info on how this compares to the 1985 version. I have catacombs and heroes for dungeonquest as well.
Love the game, just need to know what is different before i sell my original copy to a collector.

cheers,

Well, for one thing, the cards aren't shaped like coffins and doors and such anymore. =P

The combat mechanic has been changed to be card-based, to the general displeasure of most it would seem (I'm fairly ambivalent myself. I'll try the card-based system a few times, although I figure there's a good chance I'll end up looking into a dice based variant if only so I can make homebrew versions of all the other heroes in Terrinoth without needing to make a set of homebrew power cards for each.)

There's a new "sun track" that imposes a time limit on the game, although it seems like it's plenty long enough that you'd probably be dead in the old edition if you stuck around the dungeon that long anyway.

Monsters have tokens that hang around if they aren't killed. It's been a while since I played the older version, but I don't recall that being the case before.

Other than that it's fairly similar to what I remember. Still as deadly as ever, anyway, and that's the part I like about it. =)

creatures never persisted in the original and the sun track was 26 turns. is the game longer or the same then?

The sun track is the same length as the last edition, though it did not have the life loss rolls near the end that current edition does (and which we ignore).