water line leak - major problem
In terms of what kind of walkway to put back there, pavers (like brick or bluestone) could be easier to remove and put back in the future.  You also can consider putting the pavers flat with the driveway, and having a step up to the porch, or vice versa, which gives you the opportunity to deepen the porch.  A 10" slab is a lot of material to replace.