The cost of a CDRW is as low as £15.00
As long as you have an IDE lead already, you really shoulnd't need anything else.
Disconnect the mains power cable.
Slide the side of the case off, (depending on the make and model of the PC, you maight have to take the front facia off too), disconnect the power and IDE cables from the drive, unscrew the drive and slide it out of the front.
Look on the back of the removed drive to check the jumpers.
Set the the new drive's jumpers to match, slide it in, screw into position and reconnect the cables.
Reconnect the mains power cable.