I did 3 of mine last year - very easy job.

The door is extremely heavy, remove the sliding door to ease handling.
Make sure the slider is reattached and closed BEFORE nailing on the flange
Fill the gaps with insulation or use the special low expanding foam for
windows. The regular stuff expands too much and may crack the glass.
Use plenty of caulking to seal the trim around the cutout for the flange.
I was able to remove the siding, by pounding the nails thru with a punch,
so I did not have to cutout for the flange on 2 of the doors.