Complete and true needs help with replacing a item

[Icedcamper]

Im trying to replace a basic pistol in Jericho house in megaton,but I keep getting a error

 

Form's ID is not unique!

Previous form is type weapon.

 

Since im very new at this,I have no idea what that means. Ive torn the help site and the web and these forums apart looking for a answer,can anyone help me? Thank you ahead of time

 

 

Edit:Title is supposed to say "Complete and true Noob needs help with replacing a item. My bad

[CowgirlFromHell]

It's quite simple.

 

Select the weapon you want to replace it with in the "cell view" window via double-clicking on it. Then right click on the name of the weapon in the "cell view" window and select edit. Then in the window that pops-up, click on "Edit Base". Then at the top left of the new window that pops-up, there's the word "ID" and a box with the "ID" of the weapon in it. Change the "ID" to whatever you like that's not already taken. I.E. "Weap10mmPistolSpecialVersion" or "Weap10mmPistolKickAssVersion"