Hi Michael,
If you are having SAP GUI 720 look into note "1425805 - Hardware&Software requirement for BW 7.x Frontend in GUI 720".
MS Office 2013 is supported by Bex tools as of FEP 1000 which is released as of CW 09, 2013.
I assume as of GUI 73 it is supported as probably mentioned in the note 1085218 but note as it self if only internal for the time being.
Cheers, martin