Contact the Mercedes Dealership and give them the vin for your car. The radio code will show up on the 'VMI' They may ask you to drive the vehicle in to show proof of ownership but they should get the radio working again for you at no charge. Do not just enter random numbers or you will lock the radio and may have to wait up to 1 hour for it to unlock so that the radio code can be entered again.
assuming it is right hand drive the logical place for the hood release is on the left side of the passengers seat just under the dash http://www.mercedesmedic.com/wp-content/uploads/2016/02/open-hood-mercedes-benz-release.jpg
I recently had my engine replaced in my 2002 grand marquis 4.6 with a 2009 crown Vic 5.4 engine and was running fine until I broke my ignition and tried to replace it myself I bought a new ignition switch didn't work so I bought a steering column and still won't start what do I do
Assuming you didn't drill the lock, it would have been best to access the interior of the vehicle (if not deadlocked, breaking in would be relatively simple) and current could be supplied to the vehicle via the cigar lighter or from under the hood by connecting to the battery circuit in order to use the in-car trunk release if fitted.
A way into the trunk can usually be found by removing the rear seat or hooking the keys using a fishing tool through the armrest aperture if there is one.
P0300 indicates a random misfire - a misfire that is not consistent and not confined to one cylinder.
Worn/faulty spark plugs, failing coil(s) or coilpack, wiring, connections...
Fix that and the other codes will probably disappear.
For Old Models of Mercedes-Benz: The traditional digital clock on older Mercedes-Benz models will be changed by the press of 2 buttons. They are either close together on the radio console or spread far apart on the driver's display behind your wheel. On the radio, 1 button will add hours, and the other will add minutes. On the driver's display, you need to hold the left button down. That will cause either the hours or minutes on the digital clock to flash. Then, the right button will change the time. Hold the left button down again to switch from hours to minutes to off. For New Models of Mercedes-Benz: Most recent Mercedes-Benz models will have a digital screen above their transmission. Sometimes it has menu buttons on the side, other times it is a touchscreen. Luxury cars should be packed with technology and convenience of course. These are used for either basic sound systems or more complex infotainment systems. Simply go to your home menu, find the settings, and go into the display. You should easily be able to find the clock and time settings and then change them. Additionally, depending on your model, some infotainment systems are connected to satellite and/or internet data and may change the time automatically for your ease and comfort.