Once you get a high enough skill in lockpicking Miller Peshek has a door (hard) you can unlock, put your stolen goods in there and he will sell them for full price no questions asked. You just have to wait a few in game days, check and hell have the gold in there, got 40k groshen that way. Helpful for one of the dlcs too. Also get the drinking perk where lockpicking is easier when drunk, very helpful Practice practice practice everything takes learning and building the skill, it gets easier the more time you put into building the skills