How close do I really have to place a 25MHz crystal?
7 mm between a 25 MHz crystal and the chip driving it is no big deal.  What is far more important is that the ground side of the crystal caps connect back to a ground pin on the part, not just punched thru to the ground plane.  You don't want those high frequency currents running accross the ground plane else it will become a center-fed patch antenna.  All the ground pins and other immediate ground connections to the chip (like the crystal caps) should be connected in a net with lines as short as you can manage, then that net connected to the main ground in one place only.  This keeps all the little high frequency currents local, with only the external currents flowing accross the ground plane.