Good luck.

That leakage plus the age means it's time for new batteries. To dispose
of the old ones properly, many auto parts houses will accept them for
recycling. There's also many public agencies that take them as well.

Don't try to get by with just replacing the leaker, do the whole set.

http://www.panasonic.com/industrial/battery/oem/images/pdf/VRLA_LC-MS...

The battery contains H2SO4 or sulfuric acid. Sulfuric acid eats denim on
contact (1 second of contact is enough to leave a permanent hole
as you'll discover after wash day). Sulfuric acid will also attack
skin, although the effects may take a bit longer to be realized.
If you touch it with paper products, the paper turns black almost
immediately. In the lab, a paper towel makes an excellent test
for an acid spill. (We used up to 12M solution in the lab.)

The MSDS recommends sodium bicarbonate as a neutralizer.

Bicarbonate is also listed here, in "Maintenance Precautions".
It seems the more benign of the two things suggested.

http://en.wikipedia.org/wiki/Lead-acid_battery

My primary concern, would be avoiding the acid, and in doing
so, you're likely to stay clear of the lead as well. The
MSDS lists Pb, PbO2, PbSO4, H2SO4 as the stuff in the battery.

Place in a leak-proof plastic tub and transport out of your
residence. (If you can safely pick up the battery now, I
would transport first, and neutralize it once outside. Then
any home chemistry accident is likely to have less collateral
effects.) And don't try and neutralize the entire battery
contents. Take it to a battery recycler, as they probably
already have an acid mess on their hands.

If there are any exposed electrical contacts, they should be
insulated. The last thing you want, is some metal object
touching (+) and (-) and starting a fireworks show. The
battery in a UPS, should be designed pretty well in that
regard. Unlike an automotive battery, which is a
disaster waiting to happen.

    Paul