Advice, eh? Well, I would pick up the module, slowly tear it in two. Toss it in the wastepaper basket and light it . . .
But seriously,
As a player running through this module I thought it sucked horribly. You have to take great pains to generate sufficient player hooks, b/c the module itself is certainly no help.
Some mistakes our DM/module made,
1) There are no contingencies for using high-level divination magic. For instance, after the Bat-person adept (leader, forgot his name) was slain by assassins, our cleric simply Resurrected him. No harm done...
2) We scried on the assassins, having seen them and all. They were in the Fire Salamander citadel. We then proceeded to cast every buffing spell on the party, 'ported in with total surprise and laid waste to the entire establishment in record time.
Some tactical decisions that our DM made that were *good*:
1) The Beholders are potent, but relatively easily to dispatch *if* you can get behind them. Therefore, make every effort that the Beholders allies keep their foes *in* the anti-magic cone. If the PCs are human and therefore have magical darkvision, they are very screwed. Make sure you isolate foes and try to take them down don't spread yourselves to thin.
2) Re-think the spell selection of the NPCs carefully. Skip didn't put too much care in this it seems.
3) One of the more potent uses of Wish for the Efreet would be to use Planar Ally to summon a Pit Fiend. Tell the Fiend that it can have all the party's treasure (which should be a ton) if it can dispatch them. Since this spell actually brings the creature to the Prime (Rather than summoning it), the party gets XP for defeating it.