Down the main way along the river a bit from the Boatmen's Tavern is an old ramshackle hovel hung with crude trinkets that glitter and jingle in the wind and rudely scrawled over in faded red paint with "Cugel the Wise". It's not much to look at, and neither is the proprietor.
Cugel is usually clean, but he smells and looks of poverty, his clothes mostly rags except for his hat, which is a nearly ridiculously large and floppy thing with a very gaudy hatband ornament that looks like a piece of cheap mother-of-pearl. His wares are almost without exception trash, though he swears up and down they're potent magical charms of all sorts - against illness and scrying and for love and against magics, etc. etc. If someone were to actually take the time to poke through all of it, and had an eye for such things, he just might (5 or less on 3d6) find something of actual value, though Cugel is unlikely to part with it without charging far more than its worth.
Cugel is a rat and a scoundrel who spends most of his time and money at the Boatmen's tavern cheating at cards and shilling his useless trinkets to the gullible. However, one thing he does have is information, and pretty much all the natives will vouch that, in this particular, he is both accurate and honest.
Given a day and $100, he will answer any question about the Temple and its surrounds. His answers won't always be complete, and very seldom they will be, "I don't know," but they will always be accurate.
Cugel's relevant skills, if they need to be rolled for some reason instead of just giving the information, include:
Area Knowledge (Temple of Elemental Evil) - 18
Hidden Lore (Temple of Elemental Evil) - 14
Hidden Lore (All other specialties) - 16
History (Temple of Elemental Evil) - 18
A note on price: I'm trying to set a price that's low enough Cugel might be approached, but high enough the PC's won't just dump cash on all their problems. It's open to adjustment, especially based on the local economy.