You can play Heroquest with Advanced Heroquest rules using the Heroquest board, and you get a much more di diverse set of monster models with Heroquest, so I would suggest that you purchase that. If you need the rules for Advanced Heroquest, and can't find them anyway, send me a PM between 15th-22nd September, as I can help you out with that during that week.
When I say that Heroquest really is too easy for the heroes, it's way too easy. Monsters only have a one in six chance of successfully saving themselves from death, and apart from the Ogres in the Ogre horde supplement, and the wizards in Wizards of Morcar, they all only have one wound. Heroes have a two in six chance of saving themselves from being wounded and have multiple wounds. They also have access to much better equipment, and can find things like healing potions and gold very easily.
Advanced Heroquest allows the GM more scope, has a richer narrative and quest ideas, and has a very enjoyable character generation system for people involved in the campaign to use to create their characters should they wish to do so.
In terms of integrating the two. Here's how it works. The rules for Advanced Heroquest replace all the Heroquest rules, except for board and room generation. Because Heroquest is played on a fixed board, you don't roll for passages, room type, or anything like that, you just plan out the Heroquest board in advance on a piece of paper. You can also do it on the computer, but the program which used to be great for this no longer works properly, as it hasn't been updated in a while. If you want to give it a try, you can download it here:
http://www.heroscribe.org/heroquest.html.
There are a few other rules which are modified or tweaked to fit in with the Heroquest board, such as the large monster rule not being used, and certain traps working slightly differently, but on the whole, things are pretty straightforward to implement.
Some other links that may be of help are my old topic from WarSeer and Greywolf's Advanced Heroquest page:
http://www.warseer.com/forums/showthread.php?137613-Advanced-Heroquest-amp-Heroquesthttp://greywolf.critter.net/ahq.htmPlease let me know if you need anything else

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