Look on the inside of the DS arm and look for a model#. It should be something like FC-Mxxx.
It appears the crank you linked to requires a 122.5MM BB. Your existing crank may or may not use the same spindle length.

You could probably get it to shift with your current FDER, but expect it to be less than stellar.
It'd be better to spend the $15 or so for a FDER designed for the larger rings.