Unless a part is clearly marked as being "Made in" it is impossible to prove where it came from. Keep that in mind as others join the conversation.
I believe that furniture only counts as one part altogether also but others will weign in as well.
I was a bit confused by your post...are you looking for wood to replace your plastic? Also you mentioned "before you sell it" so are you selling the rifle or replacing the plastic furniture then selling that?
I have some furniture still lying around if you are interested in making up your own or refinishing it to have a certain look. Others will likely also have as well.