Now you have removed the heatsink clip you can remove the bottom cover to reveal the circuit board to desolder the transistors. I should add that as Dieselman has helpfully reminded us quite frequently these ECU ignition out transistors overheat due to problems with the ignition coils or their low tension supply wiring from the ECU to the coils themselves. This is often due to thermal stress causing wiring insulation breakdown or bad connections in the ECU plug. After you repair the ECU it would be a pity if that work was wasted by the original fault causing a second failure. Have a good look at the wiring and check the coils since they are a very common failure on that engine. On 4 cylinder cars One coil fires 1 and 4 and the other 2 and 3 plugs. If there is evidence of coil failure replace it. Once more I should acknowledge Algorithmus contribution to this thread by the use of his pictures. So if you have an old VDO W124 ECU with burned out ignition control transistors and you fancy your chances with a soldering iron--------what have got to lose ???????????