You can't go from Undead to Fey, check The Type Pyramid in Savage Species, page 142. Relevant portion:
Construct, Outsider, Undead: These three types reside
at the top of the pyramid. Once a creature becomes an
undead or a construct through the application of a template,
it cannot become something else. Once a creature
stops being a native of the Material Plane, it becomes an
outsider and stays one.
The only way to not be undead any more would be through some sort of resurrection effect, in which case you would lose everything gained from the undead templates, including Evolved Undead.

Get the feat Extraordinary Spell Aim in Complete Adventurer. Get Persistent Spell with either Incantatrix 4+ or Divine Metamagic: Persistent. Get a Starmantle Cloak from BoED. Cast a Persistent Antimagic Field every day, using Extraordinary Spell Aim so it doesn't have any affect on you, your spells, or your attended items. Any attacks made against you will be under the effect of the AMF and considered a nonmagical weapon, which the Starmantle Cloak will automatically destroy. It doesn't matter if an attack is made with a manufactured weapon or a natural weapon, both are weapons and both will be destroyed by the Starmantle.

Get Epic Spellcasting for your level 21 feat. Create an epic spell that takes enough other spellcasters to contribute spell slots to for it to have a DC of 0. The time it takes to research is multiplied by zero and occurs instantly. The cost to research it is multiplied by zero and it's free. The spell has an instantaneous duration, just like using Wish to increase an ability score, so it cannot be dispelled and its effect cannot be suppressed in any way. The spell's effect is the Reflect seed for melee attacks, you spent a thousand years casting it every day, each one has five charges, so you can reflect a total of 1,825,000 attacks before it gets used up. Every time this opponent attacks you, the attack is instead reflected back on him, damaging him instead of you. There is no way to overcome this effect apart from either not making melee attacks against you or by attacking you enough times to exhaust the number of charges.