If you really want to do a good job taking out your sod, you don't want it to take you forever and then consider using a sod cutter rental. Usually a rental is a pretty good price, kids you can get one for about $50-$60 for four hours. This should give you plenty of time to cut away most of your sod. Before you turn the sod cutter on, make sure that you know how to run the machine forward and in reverse. Also make sure that you never have your cutting blade in the ground when you are going in reverse. Before you begin, you are also going to want to know what setting or what depth to adjust your machine to.
The best way for you to go if you are just going to get rid of the sods is to go down about three quarters of an inch. This will cut far enough so that the grass will hold together, but you won't have to haul away any extra soil. Also, if you're just going to be replacing the grass with you sod, this is probably a great depth so that you don't have to add more soil or re-create. Before putting down new soil, make sure that you put down a thin layer of topsoil. Also it wouldn't hurt to add some starter fertilizer just underneath the sod. This will help the roots to establish themselves faster and help your lawn to come back.
The most important thing you can do when you're laying sod is to make sure that all of the edges are up right next to each other. Then, you want to keep the sod from drying out. Water it as often as you need to keep it moist so that the roots have the best chance of growing and so that your sod doesn't dry out.