Turned off power to in-counter oven at the breaker box. Removed the oven door (slides up and off) and 2 oven racks and then used socket and ratchet with a long extension to remove 2 small screws holding the failed element's mounting bracket to the rear of the oven. Gently tugged and tried to work the element's tail with wires attached by slip-on connectors through insulation and hole exposed after removing screws from the element mounting bracket. Despite care, one wire's slide-on connector pulled off of old element and was irretrievable from inside the oven. Then removed 4 perimeter screws with a medium Phillips screwdriver holding the oven in the opening position and slid the oven out of the counter opening and placed it on a mat on the floor. Removed the covers with the same socket and ratchet from the back of the lower oven area to expose the wiring. Then routed inadvertently disconnected wire through the opening into oven. Installed new oven bake element by sliding both wire connectors onto element's spade lugs and crimped each firmly with pliers to assure a good connection. Tugged to assure they were well attached. (The wire connector on the "lost" wire showed signs of poor connection and minor arcing.) Reinstalled oven by reversing steps.