PolyRenewal foam injection for settling slab foundation

Question

My house is built on a concrete slab foundation and is 20 years old. Part of the slab, roughly 15'x6' in size under the kitchen, is cracking off from the rest of the foundation and settling down. In some parts inside the kitchen, edges of the settling can be felt with bare feet through vinyl sheet flooring, with measurements showing up to 0.25" of settling. There are 3 cracks visible outside the house, right outside the kitchen. These cracks visible outside the house have existed for many years, but the 0.25" settling inside the kitchen is recent and relatively sudden. A foundation repairman is recommending PolyRenewal foam injection by drilling penny-sized holes through the kitchen floor, to raise the settling part and prevent further settling. While the foam injection itself costs $1,600, the flooring inside the kitchen will need to be replaced at some point after that, which will add to the total cost. I have a couple of questions, if someone with experience with this sort of thing can advise. (1) Given that the settling is only quarter an inch, what are the risks of leaving the foundation alone and doing nothing for now? (2) If I move forward with foam injection, what are the risks of that? Will home resale value be affected if such foundation repair is done? Thanks!