From the Heal Spell, "The character can use the Divine or Primal magic skill in place of a Medicine check in order to remove damage or heal Critical Injuries." Does that mean the character has to follow the Medicine rules for healing? I.E. Would it be an Average Check if the target has current wounds equal more than half of wound threshold? Or is it only an Easy Check as per the Heal Spell text? Cheers!

Edit: Would this also apply to Critical Injuries, meaning you could only Use Heal once a week to try to fix it?

To quote the next sentence: "When making the check, the character selects one target they are engaged with who is not incapacitated. The default difficulty of the check is Easy (D)." - GCRB pg. 217.

My reading has always been that the Heal spell action defines the difficulty to heal Wounds. The additional effect "Heal Critical" allows you to heal a Critical Injury with a +2 increase in difficulty. So a Heal spell with no additional effects is an Easy (D) check, and Heal spell made to heal a crit is Hard (DDD).