Drive that car for a while with a blown head gasket and it will only get worse. Eventually it will blow fully and the car will overheat any time you drive it. As mentioned above, do the head gasket at the same time as the timing belt. It would be silly to go that far in and leave the leaking gasket. It's just a timebomb.
As for the price, wheel bearings are freaking expensive to get done and it's one of the few things I only trust the dealer or a Subaru specialist to do. Anyone who tells you they can do wheel bearings on a Subaru without the special tool are setting you up to be back in there a year later replacing the wheel bearing they messed up on installation.