I'm not familiar with silvia's construction nor operation but I'll take a stab at this, as I just replaced the light in my machine. (I thought the light on the silvia was inside the switch but i could be mistaken. Either way, its the same procedure to replace a switch or a light). Be warned though, you will probably void any existing warranty and any harm that may befall you is only your responsibility. Anyways... Basically, unplug the machine, and remove casing panels on the machine until you can reach the dead part. Take a photo or draw a diagram of the wiring, noting colors and position of wires. Disconnect wires from the part and then it should pop out by squeezing some kind of retainers on the part. Sometimes those retainers can be pretty stiff, and easiest just to cut them off and pop the part out. Then do all of this in reverse for the installation of the new part. I would test it before putting the panels back on, just to make sure everything got hooked up properly.
To find replacement parts, look on espressoparts.com or if you need them in a hurry, you can find substitute parts that will function the same but may look slightly different at an electronics supply store or maaaaybe at a radioshack. Good luck! Any other questions, just throw them at us!
Edit: here's what you are looking for:
http://www.espressoparts.com/R_1026 or
http://espressocare.com/Qstore/Qstore.c...ator+Light This is really a generic/common part though and you could most likely find a similar if not identical part at your local electronics supply store.