Definitely read Nanci's caresheet, it is really excellent. Here are my thoughts on heating, and it has served many of us well over the years.
Your warm end (covered with a hide) should be about 85° or so, and the gradient heat will cool off toward the cool end which will be around 75°. Put as many hides in the viv as possible so the snake can choose where he wants to be.
Ditch the lamp. It costs more in lightbulbs that in is worth, it can cause fires and it dries out the viv. Get a UTH made for your size tank and put it under the glass on one side, cords out, and it should cover about 1/3 of the bottom. Corns aren't basking snakes, they use belly heat to help digestion.
Set it to 87° and use a separate digital probe thermometer to ensure the thermostat is reading correctly. This should be placed under the aspen, on top of the glass directly over the middle of the UTH.
Human heating pads are NOT recommended at all, no way to control the temp, and even a UTH won't make the section of the viv warmer if it is on the side.
Good luck!