We have had our old back boiler and fire taken out and want to install a solid fuel fire - HELP!?

We don't know how to go about doing this and wondered if anyone had previous experience of it. There is currently a whole in chimney brest with NO fire back etc. and an old circular flue hanging down the chimney !. I am looking at purchasing a cast iron fireplace and would dearly like to have a real fire on Christmas morning - any help much appreciated. We don't have huge amount of money to be able to pay someone to do it for us but realize that we may need some professional help along the way.