This quest can be acquired from Miller Woyzeck at his mill north east of Rattay. Once you have it, make your way to Talmberg and be sure to unequip any armour with high noise and vis/conspic ratings. The guards are most numerous during the day and in the evening, so it is a good idea to wait until night falls, some time after 11, before you attempt to steal the waffenrocks.
Once you have the waffenrocks exit Talmberg before fast travelling to avoid any incidents with guards wanting to search you. Take the waffenrocks back to Miller Woyzeck to initiate the next phase of the quest.
Ask for another job from Miller Woyzeck to receive the task of stealing a horse from the Merhojed stables. Make your way to the stables and look in the northern fields for the horses which are furthest away from prying eyes.
With no one around, mount and steal the horse. Ride the horse back to Miller Woyzeck and keep to the roads to avoid being dismounted. When you reach the mill, dismount and speak with Woyzeck to recieve the reward.
Speak with Miller Woyzeck again to receive the next objective in the quest. Once you have been informed to steal jewellery from Lady Stephanie's bedroom, make your way to Talmberg. You should wait for daylight (after 9am) before you attempt to enter the bedroom.
Take the jewellery and deliver it to Miller Woyzeck to complete the objective and the quest.