What you should do is excavate and then:
1. put down landscaping fabric. This is a tight weave material that
won't rot due to exposure to moisture in the ground. It's purpose is to
prevent the limestone from dissipating into the soil to prevent soft
spots in either the asphalt or concrete you put over top.
2. Spread crushed limestone over the area you intend to pave or place
concrete over. Typically, the limestone will be anywhere from 3 to 4
inches thick and will be compacted down to 2 1/2 to 3 inches thick with
a plate compactor you can rent.
3. Put your rebar in. Ideally, it's best to put in TWO layers of rebar;
one layer near the top of the slab and one near the bottom. That way,
for the slab to bend far enough to break, the rebar has to stretch.
Since steel is very strong in tension, it's the rebar's resistance to
stretching that makes the slab more rigid and resistant to bending.
Where you only see one layer of rebar supported in the middle of the
slab, it's not there to strengthen the concrete, it's only there to
prevent the pieces of concrete slab from spreading apart when (not if)
the slab breaks. You can buy supports for rebar at any place that sells
rebar. Look under "Steel" or "Concrete" in your yellow pages phone
4. HIRE someone to finish your concrete for you. You can save 90
percent of the cost of the job by doing all the bullwork yourself, but
placing concrete and finishing it is a skill that takes a lot of
experience to master. And, with concrete, any screw ups are permanent
screw ups. Do all the bull work yourself, and then hire a concrete
contractor to actually place the concrete for you, and you'll end up
paying less for a professional looking job.