Under Dash water leak

as far as sealant is concerned i would call the local glass companies and see if someone will sell you a tube of urethane brands like sika, essex, and titan will do you well. you can also use the stuff from the auto parts store, it just costs a little more. a word to the wise always use gloves and if you get any on a visible body panel use the "hand scrubs in a bucket" that are readily available at the parts store. those will take off the urethane without exposing your paint to harsh chemicals.