I found some info on this site...
http://cr4.globalspec.com/thread/14899/Leaking-battery-stuck-in-Mag-Lite#comment150608
"Sadly, when a dry cell leaks, the leaking chemicals react with the torch casing, as you have noted.
With all Maglite torches I have ever seen, you can remove both ends of the cylinder which encloses the batteries.
In this situation, get a broom handle or wooden dowel, just a bit
smaller than the torch battery diameter, and after soaking the
cylinder/switch assembly cylinder in hot water (boiling if you can) for
an hour or two, give that inserted dowel a few taps with a large hammer
or mallet.
Normally the leaking battery comes out easily, providing you let it
soak in hot water long enough to soften the corrosion products.
Once you have gotten out that battery, leave cylinder soaking
overnight, and use an old toothbrush to remove the last of the oxide
etc , and allow to dry thoroughly.
As a tip for next time - to save you all this bother: Oil or grease
the inside of the torch cylinder, and re-coat with oil (silicone grease
is best), each time you replace batteries.....
"
hope this helps you.