Label all the lines that currently enter the electrical panel. There will be three lines for every breaker connection in the panel. There is a hot connection on a black wire that carries the power, a neutral connection on a white wire that is the return line and a ground line on a green wire.
Take out the breakers from the panel once the labeling is finished. Once you have removed all the breakers, disconnect the ground line from the ground bar. The ground bar connects to your house ground and to the neutral bar, which returns to the electric utility line.
Remove the main power breaker from the old panel, securing it so that it doesn't touch anyone or anything. Live, hot wires can cause serious damage and even kill if touched. Remove the old panel from the wall and install the new panel in its place.
Break out the entrance hole for the power lines and feed the main power breaker through the hole and attach it to the panel power bars. Wire the utility neutral line to the neutral bar and the house ground to the ground bar. Make sure there is a connection between the neutral bar and the ground bar.
Reinstall all the old breakers and lines as you go. Try to keep areas of the house together as you work through the new panel. You should now have room to add more breakers and circuits for the remodeled section of the house.