If you wander over to the Historic Aviation section of Keypublishing's discussion boards, and look at the several page discussion there, you will find that the last time someone did it that way, the plane broke into several pieces due to the deteriorated and corroded airframe, and the several tons of sand and water that had completely filled the aircraft.
They want to take their time, and make sure that they do not make anything worse while removing it... which means they will try to remove the sand from inside, while at the same time not exposing it to air very much, as metal corrodes much faster when exposed to
both air and salt water that it does when completely submerged.
Also, it is a P-38E... and the only flying E model is "Glacier Girl"... all the rest are F/G/J/L models... and there is no preserved E model P-38 in Europe at all.
http://forum.keypublishing.co.uk/showthread.php?t=75682