replacing thread to hardwood

i have a flight of stairs with a landing. it was covered in carpet and we had to rip up the carpet because of the pets. we are going to replace the existing thread which are 2x10 with hard oak hardwood.

the stairs are 48" across with the studs on the ends, the dry wall is flush with the exitsting threads. Is there a way to get the new threads in with out cutting up the drywall to pieces. I would rather not deal w/ replacing drywall.

some of the stairs, it looks like i would be able to slide the thread in the wall to place it but most of them have a stud on each side.