the globes come with a green condom, globes, easily replacable.
As for dry joints, run over all the joints with your soldering iron, might not work but it did on mine.
Speaking of which is there anywhere to get the coloured plastic backing used to turn the display green? Im trying to work out if it can be changed to another colour and what would be needed to do this
you can get ready made LEDs from Narva but it might be a mission to find.
If you can be fucked, find a 3mm led and (pending on foward voltage) 470ohm resistor (from the top of my head), solder it in series.
I cant remember how the light is dispersed in the clock, but remember leds are directional and might not be as bright as your incandescent light.