replaced Pads 3/4 times on my Juicy 3's and it's always been a total PITA.
there is no adjustment on the levers, as such.
the key is to make sure the pistons are fully pushed back before trying to put the new pads in. a BIG flat blade screwdriver is the best tool for this.
another tip I read to make it easier,which also worked for me was to unscrew the bleed screw on the lever a half turn to release the pressure.