Fiendish Codex

3.0 Core Rulebooks Edition:
Players Handbook 3rd Edition # 1
Dungeon Master's Guide 3rd Edition # 2
Monster Manual 3rd Edition # 3

3.5 Core Rulebooks Edition:
Player's Handbook: Basic Rulebook I (Hardcover) - 2 each
Player's Handbook: Basic Rulebook I (Paperback)
Dungeon Master's Guide: Core Rulebook II (Hardcover)
Monster Manual: Core Rulebook III (Hardcover)

3.0 and 3.5 accessories Edition:
DT1 Dungeon Tiles (Dungeon Tiles)
T2D corridors Lore (Dungeon Tiles)
DT3 hidden crypts (Dungeon Tiles)
Ruins of DT4 Wild Dungeon Tiles ()
DT5 Lost Caverns of the Underdark (Dungeon Tiles)
Dire Tombs DT6 (Tiles Dungeon)
DT7 Fane of the Forgotten Gods (Dungeon Tiles)

3.0 and 3.5 Edition Supplements:
Exalted Book of Acts
Complete Adventurer
Complete Arcane
Complete Champion
Complete Divine
Complete Mage
Complete Scoundrel
Complete Warrior
D & D: Cityscape
Draconomicon: The Book of Dragons
Magic Dragon
Expanded Psionics Handbook
Fiendish Codex I: Hordes of the Abyss
Fiendish Codex II: Tyrants of the Nine Hells
Frostburn
Heroes of Battle
Magic Item Compendium
Planar Handbook
Races of the Dragon
Races of the Wild
Spell Compendium
Stormwrack
Tome of Battle: The Book of Nine Swords
Unearthed Arcana

4th Edition Core Rulebooks:
Player's Handbook
Dungeon Master's Guide
Monster Manual
Core Rulebook Gift Set
Player's Handbook II

4th Edition Accessories:
Dungeon Master's Screen
DU1: Halls of the Giant Kings (Dungeon Tiles)

Supplements 4th Edition:
H1 Keep on the Shadowfell (Adventure)
H2 Thunderspire Labyrinth (Adventure)
H3 Pyramid of Shadows
Adventurer's Vault
Arcane Power
Martial Power
Forgotten Realms: Scepter Tower Spellgard (Adventure)
Forgotten Realms Players Guide
Forgotten Realms Campaign Guide
The village of Hommlet (Adventure)

Your best bet is a major gaming convention like Gencon, origin or Dragoncon - which has thousands of players and dozens (even hundreds) of dealers available in one place for you to bid. Except that one check auction sites such as eBay to see the same (or at least similar) to the articles go, then take your game to local stores to see if you can get almost the same or better ( remember an auction site will take a certain percentage of the selling price as commission.) If you can not get a better deal face to face, put up your own items up for auction.

Comics, sci-fi conventions and the game before that, I would go to an appraiser to see what they are worth. Do some research and see what issues are comparable sold and are expected to increase the future value, that way you sell in an optimal contract. Looks like you have a new hobby! Good luck.