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To hide the lines go to the View-tab of your Excel ribbon and uncheck the Gridlines check box. From the same menu you can hide the formula bar and headings as well.
To change the background select the area you want to change the background to (you can select the whole sheet by clicking the small triangle in the top left corner of your worksheet, right above the row 1 and left from the column A headers) and use the Fill Color dialog ("paint bucket") on the Home tab to choose the color you want.
When you change the fill color of the cells you might want to make sure your text color is still easy to read.