I installed this for a couple of student clients over the last month and if you choose the custom install you will find that by default, the removal of older MS Office components is selected. I seem to recall that there is a warning that changing this could cause conflicts.
The main disc is the one with the license Key on the reverse which FE refers to. The other two discs are ancillary programs which you may or may not want to install depending on your course studies. Altogether a great birthday present - enjoy!