Did ya spray it down with WD-40/Liquid Wrench,etc? (And wait 1/2 hour or so?)
Also try to get the engine a LITTLE warm before you try and get it out, Don't let it get so hot you burn yourself, Just cruise around and get up to temp and then go home and let it set for a half hour or till you can hold your hand on the work area comfortably.
Also if you can get it in there you can tap a hammer (good "tap" not to sissy and not like Arnold<g>) on the allen wrench and get somewhat of a breaker bar effect that is more effective to loosin it.
With the LONG end in the plug you have WAY more "flex" than if you could get it with the short end, You might want to try and return it and go to Sears and get the Socket type Allen to fit on one of you bigger Socket Wrenches
(And then do the "Tap" thing with the hammer,
Just start with small "taps" and work up to the point where you "feel" your gonna break somthin and bite the bullet and take it to a Mech. and let him worry about it if you can't get it out )
Remember "Righty Tighty"/"Lefty Loosey"
May do the trick