Welp, I think Krusten would be more gruff about it, but I suspect the rest would be quick to assure him that so long as he does his job, if something goes wrong, he won't be a scapegoat. Everyone involved knows the risks, and has their own share in the fault if things go south.
That said, it might be best if the mage can provide an estimation of what he can do, so that we're not expecting him to go beyond his limits.
She ponders what you said. "I will accompany you for 500 gold down payment. I will get a fair share of all the treasure and get to have first choice of any magical equipment we may find. I would also keep in my possession any magical wants of arcane knowledge found."
I parsed that last statement as 'any magical wands or arcane knowledge found', is that correct?
In any case, counterproposal: In the event this arrangement would have her walking off with more than one quarter of the total value found, she compensates for the difference with coin or trade (For instance, if the estimated value of every single item and every coin found in there added up is totaled at 100k gp, and she claims a staff and other arcane knowledge items worth a total of 50k, she agrees to give items or coinage worth 25k to make up the difference).
Is this the same wizard that brewed us the Darkvision potions? If so, she has the spell in he spellbook and could cast it on us.
We would mention we're planning to leave a week before the new moon, to get the darkest possible night for attacking. Cloud cover would work too, but it's harder to predict a few days in advance. How long would we have to wait?