My flex disc bolts take a 10 mm hex driver - torqued to 40 Nm / 30 ft lbs (IIRC). Not sure a hex key is a god tool to use here, torque is important and the old bolts might be tight if previously servcied with an air tool.
For the bearing, "special" tools are not required - a workbench vice, punch, and hammer. You'll destroy the bearing in the process, but it doesn't matter since you're replacing it. There are dust sheilds around the bearing. Loosen them with the punch and then beat the bearing off with the punch (beat around the base of the bearing in a circular motion, may require a good deal of force, but it will come off). lightly grease and Evenly tap the new bearing in place with the punch. Lightly grease the mount and push it onto the bearing.
If you didn't get a new rubber dust boot, be careful removing the old one as it may tear.
My bearing may well have been original at 250kmi. It was a little loose, but did nothing to change the performance of the driveshaft. The flex discs were older too, but still fine. They wear out from the inside-out so if you see threads or cracks they need replacement. Bolts, washers, and nuts for the flex discs are not supposed to be reused.