Nobody's going to trade, unless they their main aim is to get LTE data speeds and they were too impatient to wait for the LTE model originally.
Its easier to find a buyer for the phone outright on ebay than to find someone who wants to trade a 32gig FAST UMTS/HSPA phone for a 16gig VERY fast LTE phone.
Once you do get the International, you will probably need a new sim.