Can a property manager / homeowner charge me for something (drywall & painting of walls) without notifying us first?

Refunds on security deposits are governed by NRS 118A.240 to 118A.250.  The Landlord can withhold from your security deposit amounts reasonably necessary to repair damages, excepting ordinary wear and tear.  Minor marks on walls are ordinary wear, but gouges in walls that require patching/painting constitute damage rather than ordinary wear.  The Landlord must provide you a written itemized accounting of the disposition of your security deposit within 30 days after you surrender the property.  If you dispute the accounting, you need to put that in writing to the Landlord within 30 days after receiving the accounting.  So, I would say "no" the Landlord did not have to notify you first, he just had to notify you in his accounting of the security deposit afterwards.  Your only basis of complaint is to argue that the cost was unreasonable--perhaps painting 2 walls was excessive, although that depends on the facts of the case (e.g., was it necessary to "blend" with the existing paint?), but you would probably have to get a lower estimate from someone else to do the work to prove it was excessive.  The fact that the owner is a contractor who may be able to do the work for less out of pocket cost than some other owner does not prevent him from charging you the fair market value of the work.  Finally, there may be specific terms in your lease by which you agreed to something different on this issue, but I doubt it.