Would it be possible to take this game and modify it so it plays like HeroQuest? Like take the game components and adapt the HeroQuest rule book? Or would that be too difficult? I liked HeroQuests simplicity and it was fast paced and fun where I've been told descent is more complex and boring with lots of down time.
I'm wondering how recent your information is. Descent is now in its second edition; the rules have been greatly simplified and the play time has been reduced. If the people who told you it was complex and had lots of downtime were referring to the first edition, you may want to do some more research about the second edition to see if these concerns even still apply.
As a general rule, I have found it to be bad practice to buy one game with the intention of turning it into something else entirely. A few house rules to tweak things you don't like is simple enough, but if you have a completely different game in mind that is what you really want to play, buying something else and trying to convert it is going to be a lot of effort. You'll end up throwing out half the components and potentially buying other bits to kitbash the game towards what you want... It probably won't end well.
If what you really want is to play HeroQuest without needing to pay $300 for a copy of the actual game, I would recommend you research some free print-and-play games with similar themes instead. It's easier to re-tune a PnP game digitally, and you don't have to print components you don't want for your variant game (better than paying for pro game components that you'll never use.) The quality of print-and-play components that can be produced at home these days is not far off from what HeroQuest used anyway.
If you want real minis for your game, you can buy a selection of figures from any conveniently available tabletop war game to fill your needs.
The only down side would be quests. You'd have to make your own quests, probably, and that can be time consuming. Unless you pick a game with a random dungeon generator. =P