If there's a thief in your party, you need to get him up to expert in disarm fairly quickly. If you're running a monk, you need to get him promoted to initiate and then get expert disarm for him equally quickly. IIRC, one place you can get expert disarm is from William Lasker in the Erathian sewers, and I think there's another teacher somewhere in the Tularean Forest, which might be easier to reach.If you don't have a thief or monk, then like me, you have a slight problem. In my preferred MM7 parties (ACSS for Dark Path, APCS for Light), I only have one character who can disarm at all (the archer) and he can only get to expert when he's fully promoted. He has severe problems in the early game (e.g. Stone City and especially the Haunted Mansion) unless the party finds an object which boosts disarm.
That is still your best bet, and the best place to find a good item is to mephisto one particular chest in the Barrowdowns. (If you don't know what we mean by "mephisto," get back to us.) It's on the south side of a small mesa roughly SW of the Tavern in the NE corner of the site, quite near to where you enter from Harmondale. And a word of warning - be prepared to run for it after you've closed the chest! 
Some people will tell you that you don't need the disarm skill, because you can open chests from a safe distance with the Telekinesis spell. That's true for chests outside in the open, but not inside. The problem is that when you use TK, you need to maintain a line of sight to the chest to click on it, and indoors, you can seldom do that and stay far enough away to avoid damage when you set the trap off.
