Active job

Replace back door of home with secondhand door

Hey there. We recently brought our first home and have discovered our back door is actually an internal door (also rotten) and needs to be replaced. I've found a second hand door (red door, see photos) that has the same measurements (old door in cream with cat door, see photos) The work required to line it up well is beyond me. Seeking quotes for someone to; remove the old one, install the new one, ensure the lock works (or recommend a locksmith). Measurements of old door are wrapped in places, but 758 x 1980 and 1990 in paces. The secondhand door is 1980 x 760, jam 103 mm. Thanks!