Check the pads first but did both my rears callys with some low mileage Mk6 ones, been fine since... think I paid about £75 on fleabay for the pair callys/carriers/lines - I'd do both as the other won't be too far behind. For reference the carriers, although different in shape, are interchangeable, meaning you don't need to replace the carriers unless you really want to... you will need to do the lines though.
