Okay.. I think this fixes it all.

code/modules/reagents/chemistry/recipes/medicine.dm

@@ -102,8 +102,8 @@
 		St.volume *= St.purity
 		St.purity = 1
 	N.volume -= 0.002
-	St.grown_volume += added_volume
-	St.data = St.grown_volume
+	St.data.["grown_volume"] += added_volume
+	St.data = St.data.["grown_volume"]
 
 /datum/chemical_reaction/styptic_powder
 	name = "Styptic Powder"

code/modules/surgery/graft_synthtissue.dm

@@ -3,7 +3,7 @@
 //TBD: Add heart damage, have heart reconstruction seperate from organ reconstruction, and find a better name for this. I can imagine people getting it confused with manipulation.
 
 /datum/surgery/graft_synthtissue
-	name = "Graft_synthtissue"
+	name = "Graft synthtissue"
 	species = list(/mob/living/carbon/human, /mob/living/carbon/monkey)
 	possible_locs = list(BODY_ZONE_CHEST, BODY_ZONE_PRECISE_GROIN, BODY_ZONE_PRECISE_EYES)
 	steps = list(
@@ -21,7 +21,7 @@
 	name = "graft synthtissue"
 	implements = list(/obj/item/hemostat = 100, TOOL_SCREWDRIVER = 35, /obj/item/pen = 15)
 	repeatable = TRUE
-	time = 25
+	time = 50
 	chems_needed = list("synthtissue")
 	var/obj/item/organ/chosen_organ
 
@@ -36,9 +36,10 @@
 				O.on_find(user)
 				organs -= O
 				organs[O.name] = O
-			chosen_organ = input("Remove which organ?", "Surgery", null, null) as null|anything in organs
+			chosen_organ = input("Target which organ?", "Surgery", null, null) as null|anything in organs
+			chosen_organ = organs[chosen_organ]
 			if(chosen_organ.organ_flags & ORGAN_FAILING)
-				to_chat(user, "<span class='notice'>[target]'s [chosen_organ] is too damaged to repair graft onto!</span>")
+				to_chat(user, "<span class='notice'>[target]'s [chosen_organ] is too damaged to graft onto!</span>")
 				return -1
 
 	user.visible_message("[user] begins to repair damaged portions of [target]'s [chosen_organ].</span>")

code/modules/surgery/organs/organ_internal.dm

@@ -218,7 +218,7 @@
 				LI = new()
 			LI.Insert(src)
 			if(only_one)
-				return
+				return TRUE
 
 		if(has_stomach && !getorganslot(ORGAN_SLOT_STOMACH))
 			var/obj/item/organ/stomach/S
@@ -229,19 +229,19 @@
 				S = new()
 			S.Insert(src)
 			if(only_one)
-				return
+				return TRUE
 
 	if(breathes && !getorganslot(ORGAN_SLOT_LUNGS))
 		var/obj/item/organ/lungs/L = new()
 		L.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	if(blooded && !getorganslot(ORGAN_SLOT_HEART))
 		var/obj/item/organ/heart/H = new()
 		H.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	if(!getorganslot(ORGAN_SLOT_TONGUE))
 		var/obj/item/organ/tongue/T
@@ -254,7 +254,7 @@
 		// if they have no mutant tongues, give them a regular one
 		T.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	else if (!only_one)
 		var/obj/item/organ/tongue/oT = getorganslot(ORGAN_SLOT_TONGUE)
@@ -278,7 +278,7 @@
 			E = new()
 		E.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	if(!getorganslot(ORGAN_SLOT_EARS))
 		var/obj/item/organ/ears/ears
@@ -289,7 +289,7 @@
 
 		ears.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	if(!getorganslot(ORGAN_SLOT_TAIL))
 		var/obj/item/organ/tail/tail
@@ -297,4 +297,4 @@
 			tail = new dna.species.mutanttail
 			tail.Insert(src)
 			if(only_one)
-				return
+				return TRUE