See my answer at http://www.howtomendit.com/answers.php?id=191824 for the screws.
The lever is held down by a magnet which relies on the electronic circuitry to operate.
The wiring is complicate for such a simple device and there are two printed circuit boards. It does not seem possible to obtain a circuit or spares so repairing a fault would require reverse engineering the circuit, fault finding and replacing the individual faulty component.
Problems with this toaster seem common, see http://www.amazon.co.uk/product-reviews/B0000AE7D8/ref=cm_cr_dp_all_helpful?ie=UTF8&coliid=&showViewpoints=1&colid=&sortBy=bySubmissionDateDescending