yes if the transponder has already been programmed for another car thats it cant be re done, but the remote can be reset and reprogrammed to open/close doors more than once. Id try and get one off ebay and get someone with vagcom who knows how or take it to the
dealers to get the transponder coded.
on the key you have if its the remote type it will have your frequency on the side id stick with the same one if its 433 get a 433 key as there isnt alot of information about Leons and if they can accept both.