Question
We had a deck in our backyard, which we recently removed. There's concrete layer underneath.  We wanted to install cobble stones  and wanted to know how to go about it. We have about 1000 sq ft of space to cover and also wanted advise as to whether this could be done on our own.

Answer
How to install veneer cobbles on a driveway slab:
http://www.diynetwork.com/diy/dp_stone/article/0,2037,DIY_13792_3839667,00.html

Manufacturer of real tumbled cobbles with suggestions for installation:
http://www.cobblesystems.com

Another supplier of cobbles in New England:
http://www.stoneyard.com/stone/category/cb.html

These three have different methods of installation, so it depends on the style of cobble, the and supplier / manufacture抯 recommendation.  It is a material that is not really conducive to patios, per se, as it is a rough textured paver, more suited for a driveway or roadway.  

Having said that, it may be the style that is prevalent in your area or best matches your architecture.  In our area concrete pavers are more common, and some styles can mimic cobble, with more consistency, aiding in installation.

And, 1,000 sf isn抰 that much for a handy do-it-yourselfer.  It just takes patience, and good preparation.  Either cobbles or pavers can be installed onto an existing slab, or in a prepared area as outline in the Belgard links, below.

Belgard, a paver supplier in our area, runs a great site for the paver do-it-yourselfer.  This type of product is best bought locally, so check for your area's paver supplier.

Homeowner抯 How-to site (with step-by-step installation videos):
http://www.myoldcastle.com/installing_patios_walkways.htm

Contractor抯 How-to site (assumes you know some of the basics already):
http://www.belgard.biz/howtoinstall.htm

Paver Styles:
http://www.belgard.biz/shapes-pavers.htm

Some additional design suggestions to consider:

If you choose to mortar things down, then you抣l need that concrete base, and you are limited to it's extent, unless you wish to pour more concrete, to add walkways that match the covered slab that you described.  

You can remove the concrete areas that are not being covered with pavers/cobbles with a  concrete saw & jack-hammer, available at most tool-rental shops.  

It is best to by the paving & wall materials from the same supplier for color consistency.

I would suggest including a seat/wall or raised planter in your 1,000 sf patio, so that it doesn抰 become just a big 30x30 helicopter-landing pad, or worse ?a solar collector for heating up that side of the house to an unbearable sizzle.

Curving the edges isn抰 that difficult to do, either.  Cobbles lend themselves naturally to a less formal edge.  Use that concrete saw to cut the curved line, or add a 搒oldier?course of pavers between the curved edge of the patio and the edge restraint.  

Please use some sort of edge restraint system, if you are not using a mortar installation.  There are many edging options and manufacturers (in plastic, metal, & wood), and the cost is worth the long-term stability of the patio.  

Good luck!!  ~Marc