An incorporeal creature would be immune to the Sneak Attack dice.
The Incorporeal Subtype includes immunity to Precision damage except, specifically, when delivered with a Ghost Touch weapon; Sneak Attack is precision damage regardless of the type of damage it's amplifying.
You may be able to get around this with a ghost touch amulet of mighty fists; ask your GM if that's worth the investment to you. This is assuming that using a wand is allowing yourself to cast Cure Wounds, meaning you perform the Touch Attack with your hand, not the wand.
If the Rogue were to Cure Wounds Sneak Attack another type of Undead, such as a Zombie (because their Rapier isn't quite cutting it), it's a little less clear.
The best use-case comparison leans toward the Sneak Attack damage also being halved. To me, this is based on the Arcane Trickster capstone ability, Surprise Spells
At 10th level, an arcane trickster can add her sneak attack damage to any spell that deals damage, if the targets are flat-footed. This additional damage only applies to spells that deal hit point damage, and the additional damage is of the same type as the spell. If the spell allows a saving throw to negate or halve the damage, it also negates or halves the sneak attack damage.
However, as with anything not written out explicitly, you'll have to ask your GM how they would rule.