Select the range or the cell that you want reps to be able to enter data, right click and select format cells, under the protection tab, uncheck the Locked option.
Under review tab, click on protect sheet, and make sure that the options that alows users to change rows and columns format, inserting rows, deleting rows are unchecked.
Using a password to unprotect sheet will be a good decision. Place your logo in headers and footers (under the insert tab) instead of the sheet cells, to make sure it will be printed on all pages.