A couple things I see. On the outside, there appears to be concrete up to the house. Guessing it may have settled and now does not slope away from the house, causing water to stand against the wood, creating the damage. If you don’t fix that, it will happen again over time, so think your plan is solid. The wood at the bottom appears to be on a concrete slab. Guessing they didn’t use treated lumber, which is what is needed for contact with the slab. If you wanted, screw a 2x4 or 2X6 to the exposed studs horizontal to the slab and use a bottle jack to put tension on the wall when you cut out and replace the rotten wood. Overall, looks like some time, but structurally you should be fine once you address the issues mentioned above.