Welcome to the 1st gen leak club!

Most of these trucks have a seeping issue at the headgasket by the thermostat. I never fixed mine, it does it when it wants to. It hasn't leaked bad enough to be a stream, just a wet spot, leaving a green residue. Alot people have put in a new gasket, some still leak, some quit. I guess it depends on how bad it leaks. Mine has gone thru a cup full in the last year or so.
If it bothers you, change it! It may fix it, it may not.