I have a split level home and I need to replace a couple of stair treads. The stairway is a closed stringer stair - so I have no access to either side of the stringers as everything is enclosed by walls.
This is not my stairway, but it's similar
I'm really not sure how to approach replacing the treads - I imagine I can cut the old one out in pieces with a reciprocating or circular saw, but how would I get new stair treads in there?
This is not my stairway, but it's similar

I'm really not sure how to approach replacing the treads - I imagine I can cut the old one out in pieces with a reciprocating or circular saw, but how would I get new stair treads in there?