The puffy battery got replaced, however, more was wrong...

Mi Problema

The iPhone 3gs would not power on.

Mi Solución

The battery clearly needed to be replaced. After replacing the battery, the unit still did not power on. It was drawing power from the battery as the battery became rather warm. This unit probably isn't salvageable. Will save the battery for another iPhone 3gs repair.

Mi Consejo

Practice, practice, practice!