The problem is re-balancing the compressor/turbine/shaft assembly after you've had it apart - turbo builders spend fortunes on dynamic balancing machines - if the turbo isn't balanced proerly, it will wreck its bearings very quickly
I know they're ment to balance them but ive known friends to get turbos rebuilt by small companies for peanuts and i cant believe they balanced them, and they were fine.
Or do you know a company with a very quick turn around.
Buy a genuine Garrett rebuild kit off Ebay. Just make sure it's genuine with brass parts and not aluminium. You can probably get the seals by themselves from the same seller if that's all you're after.
You should be okay as long as you accurately mark the nut, comp wheel, and shaft. Line them all up when you bolt them together. Personally I would get them balanced for peace of mind as it only costs around £30.