Update Rooted Epic 4G to New Official Software

[DrJPS]

I have Kernel 2.6.32.9
FROYO.DK28
Hardware D700.0.5
Firmware
2.21

And I am rooted. How can I do the Sprint update for my Epic 4G?
If I have to unroot it first...how do I do that and how do I re-root it?

If I do not have to un-root it first, will I lose my rooting after the update? If so how do I re-root the updated version.