I have a silly question because I am new to Grim Dawn.
In Titan Quest, if you would combine a stone with a weapon or an armor, you could go to a “merchant” and un-combine them.
Can you do the same here with Grim Dawn? Because I didn’t find it yet.
And if yes, which “merchant” you’re going to?
Sorry for bad English. 
You “can” and the " " are there cause you will lose one or the other.
This is an option that come at the end of act 1 after you complete a quest (unsure how far you want to stay away from spoiler so not saying a lot). It will allow you for a small fee to dismantle it but you are going to lose one or the other (your choice) in the process.
It’s ok if I lose one or another. I just want to know HOW to do it because I don’t know!
. don’t worry most of titan quest features especially combining and dismantling components are right here plus a bunch of more quality of life features, you just need to play a bit little further in act 1 to find out! ! 
Well near the end of Act 1 you will have a quest to save Kasparov Apprentice.
Once that quest is complete you will have access to that option it cost some Iron bits and as mentionned you will lose either the component or the item
Ok, I have done that, but in which merchant I am going?
This I want to know. And in which city.
after the rescue part… please visit inventor Darlet just beside Kasparov by the rift gate in Devil Crossing!
-edit: you can also do this… in the crucible, if you have the DLC…
Thanks, I will try it!