Changing out a porch light is fairly simple. It is a matching game. I know you are thinking, electrical wires, SCARY! Calm down, its not scary. Just be sure to shut off the power supply at the breaker box before you start. Then it is just a matter of match black to black, white to white, and wrapping the ground wire.
shut off power at breaker box (after you have purchased a new light fixture)
put on gloves, gather supplies - new fixture, screw driver, and ladder.
remove light bulb, set aside for later.unscrew and disconnect the black, white and ground wires. set old fixture aside.
take fixture out the box, locate the black, white, and ground wire. the new fixture should look pretty close to the old one on the inside (minus the dirt and spider webs).
connect the black, white and ground wires to the ones coming out of the wall. screw the mounting plate in place(comes attach to fixture).
align new fixture holes over screw coming from the mounting plate, hold, attach decortive nut to screws.
screw in light bulb
turn power back on, make sure light comes on.
clean up mess.
enjoy your new home, she's a beaut.