It depends what you're worried about. If you're concerned about it being proven that you were part of the distribution of the document, then any of the suggestions posed so far will work. Buy a new hard drive, encrypt it, receive the document to it from a USB device (destroy the USB device afterwards). Upload to Wikileaks from the encrypted drive. Destroy the drive.
However if you are more concerned with being thought to have been part of the distribution (as that is, after all, what's going to get you raided) then you have a bigger problem. You don't care so much whether in 5 years anybody can show you were involved, you only care about right now, can you stay under the radar.
I would build a suitable alibi (get out of town) and then receive the document from the source. Afterwards, have a change of heart, convince the source that you are NOT going to host it anywhere, convince them you have destroyed the media, and lay low for a while.
Then upload it to WikiLeaks at your leisure. If your source is convinced that you didn't upload it the Man hopefully won't think so either.