'Bout the dragonfire-proofing: I'd appreciate just a bit of general starting advice to set me in the right path. The rest I'll try and do myself, hopefully it'll be a learning experience since I haven't done much bodyparting/materials stuff yet. Might pop some additional questions here though, if I get stuck for an evening or two.
Basically, you need to move all of the body detail plans and associated stuff to caste-level, then make copies of every material the creature uses and modify them to not have heat damage or ignition/melting points. It can all be done within the creature file, but it's far more efficient to use templates if you ever plan to do anything like it ever again.
Here's an example from one that I did:
[BODY:HUMANOID:2EYES:2EARS:NOSE:2LUNGS:HEART:GUTS:ORGANS:HUMANOID_JOINTS:THROAT:NECK:SPINE:BRAIN:SKULL:5FINGERS:5TOES:MOUTH:FACIAL_FEATURES:TEETH:RIBCAGE]
[BODY_DETAIL_PLAN:STANDARD_MATERIALS]
[BODY_DETAIL_PLAN:STANDARD_TISSUES]
[BODY_DETAIL_PLAN:VERTEBRATE_TISSUE_LAYERS:SKIN:FAT:MUSCLE:BONE:CARTILAGE]
[BODY_DETAIL_PLAN:HEAD_HAIR_TISSUE_LAYERS]
[USE_TISSUE_TEMPLATE:EYEBROW:EYEBROW_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:HEAD:EYEBROW:ABOVE:BY_CATEGORY:EYE]
[USE_TISSUE_TEMPLATE:EYELASH:EYELASH_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:EYELID:EYELASH:FRONT]
[USE_MATERIAL_TEMPLATE:NAIL:NAIL_TEMPLATE]
[USE_TISSUE_TEMPLATE:NAIL:NAIL_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:FINGER:NAIL:FRONT]
[TISSUE_LAYER:BY_CATEGORY:TOE:NAIL:FRONT]
[SELECT_TISSUE_LAYER:HEART:BY_CATEGORY:HEART]
[PLUS_TISSUE_LAYER:SKIN:BY_CATEGORY:THROAT]
[TL_MAJOR_ARTERIES]
[BODY_DETAIL_PLAN:FACIAL_HAIR_TISSUES]
[BODY_DETAIL_PLAN:STANDARD_HEAD_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_HEAD_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_RIBCAGE_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_RELSIZES]
[RELSIZE:BY_CATEGORY:LIVER:300]
[USE_MATERIAL_TEMPLATE:SINEW:SINEW_TEMPLATE]
[TENDONS:LOCAL_CREATURE_MAT:SINEW:200]
[LIGAMENTS:LOCAL_CREATURE_MAT:SINEW:200]
[HAS_NERVES]
[USE_MATERIAL_TEMPLATE:BLOOD:BLOOD_TEMPLATE]
[BLOOD:LOCAL_CREATURE_MAT:BLOOD:LIQUID]
[CREATURE_CLASS:GENERAL_POISON]
[GETS_WOUND_INFECTIONS]
[GETS_INFECTIONS_FROM_ROT]
[USE_MATERIAL_TEMPLATE:PUS:PUS_TEMPLATE]
[PUS:LOCAL_CREATURE_MAT:PUS:LIQUID]
[BODY:HUMANOID:2EYES:2EARS:NOSE:2LUNGS:HEART:GUTS:ORGANS:HUMANOID_JOINTS:THROAT:NECK:2HEAD_HORN:SPINE:BRAIN:SKULL:5FINGERS:5TOES:MOUTH:FACIAL_FEATURES:TEETH:RIBCAGE]
[BODY_DETAIL_PLAN:FIREIMMUNE_ADDITIONAL_MATERIALS]
[BODY_DETAIL_PLAN:FIREIMMUNE_ADDITIONAL_TISSUES]
[BODY_DETAIL_PLAN:VERTEBRATE_TISSUE_LAYERS_FIREIMMUNE:SKIN_FIREIMMUNE:FAT_FIREIMMUNE:MUSCLE_FIREIMMUNE:BONE_FIREIMMUNE:CARTILAGE_FIREIMMUNE]
[BODY_DETAIL_PLAN:HEAD_HAIR_TISSUE_LAYERS_FIREIMMUNE]
[USE_MATERIAL_TEMPLATE:HORN:HORN_FIREIMMUNE_TEMPLATE]
[USE_TISSUE_TEMPLATE:HORN:HORN_FIREIMMUNE_TEMPLATE]
[USE_TISSUE_TEMPLATE:EYEBROW_FIREIMMUNE:EYEBROW_FIREIMMUNE_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:HEAD:EYEBROW_FIREIMMUNE:ABOVE:BY_CATEGORY:EYE]
[USE_TISSUE_TEMPLATE:EYELASH_FIREIMMUNE:EYELASH_FIREIMMUNE_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:EYELID:EYELASH_FIREIMMUNE:FRONT]
[USE_MATERIAL_TEMPLATE:NAIL_FIREIMMUNE:NAIL_FIREIMMUNE_TEMPLATE]
[USE_TISSUE_TEMPLATE:NAIL_FIREIMMUNE:NAIL_FIREIMMUNE_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:FINGER:NAIL_FIREIMMUNE:FRONT]
[TISSUE_LAYER:BY_CATEGORY:TOE:NAIL_FIREIMMUNE:FRONT]
[SELECT_TISSUE_LAYER:HEART_FIREIMMUNE:BY_CATEGORY:HEART]
[PLUS_TISSUE_LAYER:SKIN_FIREIMMUNE:BY_CATEGORY:THROAT]
[TL_MAJOR_ARTERIES]
[BODY_DETAIL_PLAN:FACIAL_HAIR_TISSUES]
[BODY_DETAIL_PLAN:STANDARD_HEAD_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_HEAD_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_RIBCAGE_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_RELSIZES]
[RELSIZE:BY_CATEGORY:LIVER:300]
[RELSIZE:BY_CATEGORY:HORN:50]
[USE_MATERIAL_TEMPLATE:SINEW_FIREIMMUNE:SINEW_FIREIMMUNE_TEMPLATE]
[TENDONS:LOCAL_CREATURE_MAT:SINEW_FIREIMMUNE:200]
[LIGAMENTS:LOCAL_CREATURE_MAT:SINEW_FIREIMMUNE:200]
[HAS_NERVES]
[USE_MATERIAL_TEMPLATE:BLOOD_FIREIMMUNE:BLOOD_FIREIMMUNE_TEMPLATE]
[BLOOD:LOCAL_CREATURE_MAT:BLOOD_FIREIMMUNE:LIQUID]
[CREATURE_CLASS:GENERAL_POISON]
[GETS_WOUND_INFECTIONS]
[GETS_INFECTIONS_FROM_ROT]
[USE_MATERIAL_TEMPLATE:PUS:PUS_TEMPLATE]
[PUS:LOCAL_CREATURE_MAT:PUS:LIQUID]
There are a couple of unnecessary repeats in there just to illustrate what stays the same - i.e. the blood material is defined twice and doesn't need to be. What I did for the fireproof caste was to copy EVERY body material template, add "_FIREIMMUNE" to it, and modify the material properties so as not to be damaged by heat. I then copied the STANDARD_MATERIALS body detail plan, replaced the materials with the new, fireproof ones, renamed it FIREIMMUNE_ADDITIONAL_MATERIALS, and called it. I did the same for tissues, though I can't remember exactly why and what was different about the fireproof ones that I felt compelled to do that, so that probably isn't necessary.
Please note that if you plug this into your game as-is, it will throw you an enormous errorlog because you're missing all of my templates and detail plans.