Failing Engineered Garage Slab

My good friend Ken Salvo from New Jersey shared:

Howdy...need some advice from the Indagator braintrust.

I did a home inspection in 1999 for a very nice lady. She just called and asked me to come out to look at her garage floor. This is a 1950s garage, with a cellar below. There is a poured concrete deck, and the rebar is rusting, expanding, and is breaking the underside of the deck apart. Chunks are falling onto the floor, and some rebar is visible.

There are some cracks in the surface, in the garage, though nothing major. As is normal, most of the spalling is occurring
under the area where a car is regularly parked. Snow melt has likely seeped into the cracks, accelerating the corrosion of the
rebar - mostly directly below the car parked areas.

So I'd like to give her some advice on how to proceed from here.

• -Is this likely to be a long, slow process?
• -Should she have repairs performed NOW?
• -What are the repair options, if repairs are possible, or replacement?
• -What contractor type, engineer, etc. should be contacted at this point, if any?

I've not seen many of these garage decks, so I'm not sure of how to advise this very nice lady.
Thanks,
Ken in Joisey
p.s. We've had a particularly bad winter, with lots of snow and ice - I'm sure that melted in the garage, and has soaked into the slab - freeze/thaw stuff.

What advice do you have for Ken?