We did a number of flood rehabs in 2008 when we got a 500yr flood. Many homes were structurally sounds foundation wise, but had water 3-6' on the main floor. Your situation, while a major PITA, is not a big deal as far as longevity...provided it is fixed properly.
On homes with minor flooding on first floor, and yours is below minor IMO and experience, have the contractor remove and discard anything that the water touched/soaked into.
Baseboards
Doors/door trim
carpet
They will need to cut the drywall approximately 12" above the water line....we had to go 24" above water line since water was usually at least 12" deep and the homes sat in the summer months while homies sorted things out with insurance companies, mortaguages companies, FEMA, etc....nothing was fixed right after the waters receeded.
Remove the insulation 12" up as well since the water will tend to wick up, 3" is only slightly above the treated bottom plate they used in your on slab construction so it's no biggie and the insulation would'nt have soaked it up past 12".
Your electrical should be fine since it's a slab home, all your drops will come from the attic and down, so no wire replacement or outlet replacement should be necessary as they were not touched by water.
Your plumbing will be fine too since it is coming up through the slab at waste line drops and pex lines.....
Now, you have them bring in a flood remediator like Service Pro, and they will load the house up with fans and vaccum any standing water. They will keep airing out the area's touched by water until they are dry and meet a certain moisture requirment. At that point they will then spray eveerything down with a mold preventor/killer.
After they give you the okay, then it's back upto the contractor to fill in the blanks, patch and replace everything they needed to take out.
I'm assuming your HVAC is also plumbed from the attic so those lines will be water free and not need attention, if any are in the floor, Service Pro will address them as well.
It sounds worse than it really is, after dealing with homes with waist deep water for a period of a week, and then another 2 weeks before water receeded enough to enter, and then month to 3 months before work could begin....they can be fixed and have no problems. Anybody not versed in this is obviously going to freak out and think worst case scenario, your situation would be best case scenario because unlike our area with brown water/sewage running through homes, ou had clear water, and very shallow water at that. I would'nt have a problem in the world keeping things on track, PROVIDED above criteria is met....if the contractor does'nt want to do that, then walk away.