Let me make sure I understand your concept fully. You want a large, multi level structure with no monsters and only some low threat level traps to keep people out, and the building will be full of libraries and magical items on display?
Now, that kind of thing works in "Sword of Truth" because the protagonist was looking for a specific, world-saving magic item, but unless the characters are role-playing very well and have a similar specific target, I know my group take advantage of situation and strip the place bare. How are you planning to have this not turn into a shopping trip through a compendium of magic items? And more so, what's going to limit the PCs power once all is in hand?
My advice would be to treat the encounter like a 5 room dungeon. There has to be some reason people haven't taken things from the palace before, or previous residents haven't returned to gear up, what happened? Some traps and animated items might present a puzzle for them to get past. Some setback to keep things moving, they could be teleported outside, or the hall of magical weapons only has illusionary displays of powerful magic items, no real gear. The final challenge could be straight out of Sword of Truth, some barrier that blocks certain people or things, like no paper or steel can pass, and if they want their reward, they have to leave a pile of gear behind them.
It's a classic fantasy idea to have a castle full of gear, I'm just trying to figure out how the next gaming session doesn't involve the players declaring themselves gods.