If this is the exact same problem, my best guess is that there's been some failure on the power control board (PCB) - especially if the rest of the microwave is still working fine. That tells me its not a blown fuse, or at least probably not.
Here's my best advice. Purchasing the PCB from the retailer will likely not be cost-effective - since it will probably sell for about $20 less than you paid for the microwave originally. I couldn't even locate your model anywhere on-line, but I've had good luck on Repair Clinic (http://www.repairclinic.com/
), but you could also check Sears.com. The trick is to cross-reference the primary part number, since this same part is probably used in other microwaves other than just Kenmores. After that, you can troll for the board (if you want to wait patiently) to come up on sale (eBay, whatever).
In terms of the installation, that was remarkably easy. The cover, which is just the membrane, keypad and clock window, etc. , likely releases with just two screws at the top of the panel, and then lifts up and away from the microwave. The PCB is actually attached to the back of the membrane cover assembly. Did I mention that it is smart to unplug the microwave? After that there are typically three small screws that attach the PCB to the back of the panel membrane, and I recall there are two plugs - which just pop off. Reassemble in reverse. When I did it, it took me about 10-15 minutes.