Are you 100% sure you put the LED wiring back on correctly? Pretty easy to muck that up. Does Workbench load up from floppy? If so and you really suspect the LED might be bad (highly doubtful as that's probably the most robust part on any computer), try throwing 5VDC its way and see if it lights then. If it doesn't work one way, reverse your leads. They don't call it a "light emitting diode" for nothing as its sensitive to polarity.
