Congratualtions on your recent purchase and welcome to TS.
I can't help you with a Line-X dealer in area but appreciate the fact that you want a Line-X. They are a great bedliner and well worth the money. I think I paid $300 or so for mine.
As far as your plastic bed
liner that you have, (I assume it is plastic) you will probably have a difficult time selling it here on TS because most are so fond of the spray in liners.
Your best bet would be
ebay or the scrap yard. If you just bought the truck and knew you would put a Line-X in, why didn't your dealer take the
liner out and not charge you for it?
Good luck with both getting your new
liner and selling your old one, and again welcome to TS.