[philbuilt]

Archerynut,
Nice pond! As Eddie stated take your time and study the pond and the areas around. Personally I would add an 90 el and add a 1' piece of pipe to one side and put the other end on your drain pipe with the 1' piece pointing down into the pond. The next big rain this should fill up above the el and create a natural syphon and drain your pond to a working level.
Then I would try to dig and seal the drain pipe like Eddie stated. I have a wet spot above my pond 4' higher than water level. 15' away (a spring)
having wet spots on land is common just take your time. Remember you stated the pong is 25 years +- and still standing.
Just my 2 cents.
Phil