His second mission was for a sheep not of that fold. But of the coming era. An era near the end of time. Just as you believe, however, albeit in a different body. Isa (AS) was the manifestation of the Torah and the Injeel and shall be a follower of Qur'an and Sunnah on his arrival. This is our belief and I agree this is where we part ways with the Ahmadiyyah.
just to clarify,
We believe that a follower of prophet mohammad(pbuh) [Quran and Sunnah of course] will be given the title of 'messiah'. Jesus(as) will not return in another form as some people wrongly attribute the concept of re-incarnation to us.